Put local function in an anonymous namespace
Various compiler speedups

Moved code from IR.cpp to IR.h so that it inlines.

Added a uniquify variable names pass that simplifies Simplify,
and lets it do dead let elimination early. Also removes the int
parameter from Scope, because Simplify was the only thing using it.
Added a shared pool for small integers.
Merge branch 'master' of github.com:halide/Halide

Conflicts:
	Makefile