* Remove NEQ. NEQ is converted by the CVC parser into NOT(=(..)). This makes our...

* Remove NEQ. NEQ is converted by the CVC parser into NOT(=(..)). This makes our internal format slightly more canonical. If this change works OK, I'd like to later remove: NAND, NOR, etc.
* Move the sat headers into sat/sat.h. AST.h now contains a forward declaration of just the types it needs. This should speed up compilation.
* Reduce the number of compiler warnings.

git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@180 e59a4935-1847-0410-ae03-e826735625c1