This patch defines a new asan pass gate that is activated at -O0, in
addition to the pass that was initially activated at -O3 level The
patch also does some comment cleanups here and there.
* asan.c (build_check_stmt): Rename join_bb variable to else_bb.
(gate_asan_O0): New function.
(pass_asan_O0): New variable.
* passes.c (init_optimization_passes): Add pass_asan_O0.
* tree-pass.h (pass_asan_O0): New declaration.