Remove the extern C from glib.h

Apparently this fixes build with MSVC

Bug #103621
diff --git a/goo/glibc.h b/goo/glibc.h
index 8b372bc..ccbd873 100644
--- a/goo/glibc.h
+++ b/goo/glibc.h
@@ -7,6 +7,7 @@
 // This file is licensed under the GPLv2 or later
 //
 // Copyright (C) 2016, 2017 Adrian Johnson <ajohnson@redneon.com>
+// Copyright (C) 2017 Albert Astals Cid <aacid@kde.org>
 //
 //========================================================================
 
@@ -17,8 +18,6 @@
 
 #include <time.h>
 
-extern "C" {
-
 #ifndef HAVE_GMTIME_R
 struct tm *gmtime_r(const time_t *timep, struct tm *result);
 #endif
@@ -35,7 +34,5 @@
 char * strtok_r (char *s, const char *delim, char **save_ptr);
 #endif
 
-}
-
 #endif // GLIBC_H