Implement missing replacements when installing .pc files for win32

Implement missing replacements when installing .pc files for win32

This implements replacements for win32 makefile generators similar
to the replacement functionality in unix makefile generators.

To enable Makefile code generation for replacements in win32 makefile
generators, you must set QMAKE_STREAM_EDITOR to e.g. sed.

When building for win32, sed is normally only available in the
mingw/msys build environment and when cross compiling on unix.
In these cases QMAKE_STREAM_EDITOR is set to sed in qmake.conf.

For other win32 build environments QMAKE_STREAM_EDITOR is not set
in qmake.conf and the replacements Makefile code is not generated.

Change-Id: Ie5de5d517eafaeaa2544f1e972aec3fe11d0a6f1
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>