Add pkgconfig files for libsepol, libselinux, and libsemanage.

Having a pkgconfig files allows the pkg-config tool to be used to
query the presence of the library (or a particular version of it),
and to obtain the C flags and linker arguments to build with it.

Based on Debian patches by Manoj Srivastava <srivasta@debian.org>.

Signed-off-by: Eamon Walsh <ewalsh@tycho.nsa.gov>
diff --git a/.gitignore b/.gitignore
index c0e010f..9b7ed83 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@
 *.a
 *.s
 *.mo
+*.pc
 
 # Misc
 *.patch