Add TARGET_VERSION_EXT to pkgConfiglibName

Add TARGET_VERSION_EXT to pkgConfiglibName

The libName that is used in pkgConfig files should include the
TARGET_VERSION_EXT.

This is needed because in Win32MakefileGenerator::fixTargetExt(),
the TARGET_VERSION_EXT is added to the library name.

In Win32MakefileGenerator::processVars(), if TARGET_VERSION_EXT is empty,
it is set to VER_MAJ.

On platforms != Windows, TARGET_VERSION_EXT does not seem to be used.

We probably got away with this so far because pkgconfig files generation
for win32 was just added in 4.8 and nobody uses them yet, and because on
platforms != windows the TARGET_VERSION_EXT is not used.

Change-Id: I56f239e389f0ef926030e4c2376cadd92c4f673c
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>