[build] Improve builds with different MS Visual Studio versions.

* builds/windows/vc2010/freetype.vcxproj: Switch platform toolset
according to the Visual Studio version.
diff --git a/ChangeLog b/ChangeLog
index cc30bad..cdd6ee2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2017-09-11  Azzuro  <azzuro@team-mediaportal.com>
+
+	[build] Improve builds with different MS Visual Studio versions.
+
+	* builds/windows/vc2010/freetype.vcxproj: Switch platform toolset
+	according to the Visual Studio version.
+
 2017-09-11  Werner Lemberg  <wl@gnu.org>
 
 	* src/sfnt/ttkern.c (tt_face_load_kern): Reject format 2 tables.
diff --git a/builds/windows/vc2010/freetype.vcxproj b/builds/windows/vc2010/freetype.vcxproj
index e4f11fc..592657d 100644
--- a/builds/windows/vc2010/freetype.vcxproj
+++ b/builds/windows/vc2010/freetype.vcxproj
@@ -50,6 +50,32 @@
       <Platform>x64</Platform>

     </ProjectConfiguration>

   </ItemGroup>

+    <!--

+    Switch the PlatformToolset based on the Visual Studio Version

+-->

+<PropertyGroup>

+    <!-- Assume Visual Studio 2010 / 4.0 as the default -->

+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">4.0</VisualStudioVersion>

+</PropertyGroup>

+<!-- Visual Studio 2010 (4.0) -->

+<PropertyGroup Condition="'$(VisualStudioVersion)' == '4.0'">

+    <PlatformToolset>v100</PlatformToolset>

+</PropertyGroup>

+<!-- Visual Studio 2013 (12.0) -->

+<PropertyGroup Condition="'$(VisualStudioVersion)' == '12.0'">

+    <PlatformToolset>v120</PlatformToolset>

+</PropertyGroup>

+<!-- Visual Studio 2015 (14.0) -->

+<PropertyGroup Condition="'$(VisualStudioVersion)' == '14.0'">

+    <PlatformToolset>v140</PlatformToolset>

+</PropertyGroup>

+<!-- Visual Studio 2017 (15.0) -->

+<PropertyGroup Condition="'$(VisualStudioVersion)' == '15.0'">

+    <PlatformToolset>v141</PlatformToolset>

+</PropertyGroup>

+<!--

+    End of: Switch the PlatformToolset based on the Visual Studio Version

+-->

   <PropertyGroup Label="Globals">

     <ProjectGuid>{78B079BD-9FC7-4B9E-B4A6-96DA0F00248B}</ProjectGuid>

   </PropertyGroup>

@@ -58,73 +84,61 @@
     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug Multithreaded|Win32'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug Multithreaded|x64'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug Singlethreaded|Win32'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug Singlethreaded|x64'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release Multithreaded|Win32'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release Multithreaded|x64'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release Singlethreaded|Win32'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release Singlethreaded|x64'" Label="Configuration">

     <ConfigurationType>StaticLibrary</ConfigurationType>

     <UseOfMfc>false</UseOfMfc>

     <CharacterSet>MultiByte</CharacterSet>

-    <PlatformToolset>v100</PlatformToolset>

   </PropertyGroup>

   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />

   <ImportGroup Label="ExtensionSettings">