Makefile changes to improve the build of libstp.a. Don't include

Makefile changes to improve the build of libstp.a. Don't include
Main.or files from MiniSAT, since we don't need them, and they bring
in main() functions and zlib dependencies we don't want. Add a c-api
test to try to keep this from regressing again.
Make it easier to pass -fPIC through to the MiniSAT build.
Clean up some comments and trailing whitespace in Makefiles.

git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@1036 e59a4935-1847-0410-ae03-e826735625c1