cmake/platform/win32-gcc.cmake: IF(MINGW) is unnecessary.

This file is only included when building with MinGW.
[libmodutils] CMakeLists.txt: Removed duplicated PDB code.
cmake/macros/Win32ImageVersionLinkerFlags.cmake: New macro for adding an image version to
Win32 binaries.

The TARGET_VERSION property causes the version number to be appended to
the executable when built with MinGW, which isn't what we want.

This macro replaces the /version: (MSVC) or -Wl,etc (MinGW) flags in the
linker commands with the specified version numbers.

Updated SADXModLoader to use Win32ImageVersionLinkerFlags.

libmodutils: Removed VERSION, since this is a static library.