Emit GIMPLE directly instead of gimplifying GENERIC.

Emit GIMPLE directly instead of gimplifying GENERIC.

This patch cleanups the instrumentation code generation by emitting
GIMPLE directly, as opposed to emitting GENERIC tree and then
gimplifying them.  It also does some cleanups here and there

	* Makefile.in (GTFILES): Add $(srcdir)/asan.c.
	(asan.o): Update the dependencies of asan.o.
	* asan.c (tm.h, tree.h, tm_p.h, basic-block.h, flags.h
	function.h, tree-inline.h, tree-dump.h, diagnostic.h, demangle.h,
	langhooks.h, ggc.h, cgraph.h, gimple.h): Remove these unused but
	included headers.
	(shadow_ptr_types): New variable.
	(report_error_func): Change is_store argument to bool, don't append
	newline to function name.
	(PROB_VERY_UNLIKELY, PROB_ALWAYS): Define.
	(build_check_stmt): Change is_store argument to bool.  Emit GIMPLE
	directly instead of creating trees and gimplifying them.  Mark
	the error reporting function as very unlikely.
	(instrument_derefs): Change is_store argument to bool.  Use
	int_size_in_bytes to compute size_in_bytes, simplify size check.
	Use build_fold_addr_expr instead of build_addr.
	(transform_statements): Adjust instrument_derefs caller.
	Use gimple_assign_single_p as stmt test.  Don't look at MEM refs
	in rhs2.
	(asan_init_shadow_ptr_types): New function.
	(asan_instrument): Don't push/pop gimplify context.
	Call asan_init_shadow_ptr_types if not yet initialized.
	* asan.h (ASAN_SHADOW_SHIFT): Adjust comment.