Simplify names of lattice values. SGTUNE becomes SGT, for example.

Fix initializeConstant, now initializeInt. Fixes major performance
bottleneck.

X == Y || X->DominatedBy(Y) is redundant. Remove the X == Y part.

Fix crasher in makeEqual where getOrInsertNode would add a new constant,
producing an NE relationship between the two members we're trying to make
equal. This now allows us to mark more BBs as unreachable.

llvm-svn: 33612