asm qualifiers (PR55681)

asm qualifiers (PR55681)

PR55681 observes that currently only one qualifier is allowed for
inline asm, so that e.g. "volatile asm" is allowed, "const asm" is also
okay (with a warning), but "const volatile asm" gives an error.  Also
"goto" has to be last.

This patch changes things so that only "asm-qualifiers" are allowed,
that is "volatile" and "goto", in any combination, in any order, but
without repetitions.

	PR inline-asm/55681
	* doc/extend.texi (Basic Asm): Update grammar.
	(Extended Asm): Update grammar.

gcc/c/
	PR inline-asm/55681
	* c-parser.c (c_parser_asm_statement): Update grammar.  Allow any
	combination of volatile and goto, in any order, without repetitions.

gcc/cp/
	PR inline-asm/55681
	* parser.c (cp_parser_asm_definition): Update grammar.  Allow any
	combination of volatile and goto, in any order, without repetitions.

gcc/testsuite/
	PR inline-asm/55681
	* gcc.dg/asm-qual-1.c: Test that "const" and "restrict" are refused.
	* gcc.dg/asm-qual-2.c: New test, test that asm-qualifiers are allowed
	in any order, but that duplicates are not allowed.

From-SVN: r266859