Add a new option -flive-patching={inline-only-static|inline-clone}

Add a new option -flive-patching={inline-only-static|inline-clone}
to support live patching in GCC.

2018-11-29  qing zhao  <qing.zhao@oracle.com>

gcc/ChangeLog:

	* cif-code.def (EXTERN_LIVE_ONLY_STATIC): New CIF code.
	* common.opt: Add -flive-patching flag.
	* doc/invoke.texi: Document -flive-patching.
	* flag-types.h (enum live_patching_level): New enum.
	* ipa-inline.c (can_inline_edge_p): Disable external functions from
	inlining when flag_live_patching is LIVE_PATCHING_INLINE_ONLY_STATIC.
	* opts.c (control_options_for_live_patching): New function.
	(finish_options): Make flag_live_patching incompatible with flag_lto.
	Control IPA optimizations based on different levels of
	flag_live_patching.

gcc/testsuite/ChangeLog:

	* gcc.dg/live-patching-1.c: New test.
	* gcc.dg/live-patching-2.c: New test.
	* gcc.dg/live-patching-3.c: New test.
	* gcc.dg/tree-ssa/writeonly-3.c: New test.
	* gcc.target/i386/ipa-stack-alignment-2.c: New test.

From-SVN: r266627