Patch from Khoo Yit Phang.

Patch from Khoo Yit Phang.

Clean up scripts/configure, and add flags to set CC and -fpic.
- Use POSIX shell parameter expansion when parsing flags, instead of expr.
- Fix the test for $CC/$CXX to work when they contain spaces (e.g., "gcc -m32").
- Export flags in config.info to ensure that the entire build, including recursive Makefiles, consistently use the given flags.
- Don't create the installation directories when configuring; do it when installing.
- Remove minisat configuration flags from scripts/configure, since they are unused.

git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@1127 e59a4935-1847-0410-ae03-e826735625c1