Split the C preprocessor from wrc into a separate library.
Prefixed exported functions by 'pp' to avoid namespace conflicts.

diff --git a/configure.ac b/configure.ac
index f064a98..926e021 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1378,6 +1378,7 @@
 tools/winebuild/Makefile
 tools/winedump/Makefile
 tools/wmc/Makefile
+tools/wpp/Makefile
 tools/wrc/Makefile
 tsx11/Makefile
 unicode/Makefile])