PR inline-asm/52813 revisited

PR inline-asm/52813 revisited

The original patch for this PR made it an error to list the stack
pointer in the clobber list of an inline asm.  However, the general
feeling seemed to be that going straight to a hard error was too harsh,
since there's quite a bit of existing code that has the clobber.

This patch implements the compromise discussed on IRC of making it
a -Wdeprecated warning instead.

2019-01-15  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR inline-asm/52813
	* doc/extend.texi: Document that listing the stack pointer in the
	clobber list of an asm is a deprecated feature.
	* common.opt (Wdeprecated): Moved from c-family/c.opt.
	* cfgexpand.c (asm_clobber_reg_is_valid): Issue a -Wdeprecated
	warning instead of an error for clobbers of the stack pointer.
	Add a note explaining why.

gcc/c-family/
	PR inline-asm/52813
	* c.opt (Wdeprecated): Move documentation and variable to common.opt.

gcc/d/
	PR inline-asm/52813
	* lang.opt (Wdeprecated): Reference common.opt instead of c.opt.

gcc/testsuite/
	PR inline-asm/52813
	* gcc.target/i386/pr52813.c (test1): Turn the diagnostic into a
	-Wdeprecated warning and expect a following note:.

From-SVN: r267941