extend.texi (Extended Asm): Clarify that overlap between asm-declared register...

extend.texi (Extended Asm): Clarify that overlap between asm-declared register variables used in an asm and...

	* doc/extend.texi (Extended Asm): Clarify that overlap between
	asm-declared register variables used in an asm and the asm clobber
	list is not allowed.
	* stmt.c (decl_conflicts_with_clobbers_p): New function.
	(expand_asm_operands): Keep track of clobbered registers.  Call
	decl_conflicts_with_clobbers_p for each input and output operand.
	If no conflicts found before, also do conflict sanity check when
	emitting clobbers.

From-SVN: r57437