[build] Really fix multi and C++ builds.

The following builds were still failing due to previous changes:

  make multi
  make multi CC="c++"
  make CC="c++"

This patch fixes the issues, which were missing includes to get the
right macro definitions in multi-build mode.

Also, `FT_UNUSED' is actually used by third-party code, so move it
back to `public-macros.h' to avoid breaking it.

* include/freetype/config/public-macros.h (FT_EXPORT): Remove
special definition for C++.
(FT_UNUSED): Define here instead of...
* include/freetype/config/compiler-macros.h: ... here.
(FT_FUNCTION_DECLARATION): Remove special definition for C++.
(FT_LOCAL_ARRAY_DEF): Fix definition.

* src/cache/ftccback.h, src/lzw/ftzopen.h, src/gxvalid/gxvmort.h,
src/gxvalid/gxvmorx.h: Add `FT_BEGIN_HEADER' and `FT_END_HEADER'.
7 files changed