Expand %= into ${:uid} so that the code generator emits a unique ID for the

Expand %= into ${:uid} so that the code generator emits a unique ID for the
asm.  This allows us to properly handle the case when an optimizer duplicates
the asm, such as here:

void bar() {
  int i;
  for (i = 0; i < 3; ++i)
    asm("foo %=" : : "r"(0));
}

we now produce:

_bar:
	xorl	%eax, %eax
	## InlineAsm Start
	foo 0
	## InlineAsm End
	## InlineAsm Start
	foo 1
	## InlineAsm End
	## InlineAsm Start
	foo 2
	## InlineAsm End
	ret

instead of:

_bar:
	xorl	%eax, %eax
	## InlineAsm Start
	foo 1
	## InlineAsm End
	## InlineAsm Start
	foo 1
	## InlineAsm End
	## InlineAsm Start
	foo 1
	## InlineAsm End
	ret

This also fixes a fixme by eliminating a static.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@66528 91177308-0d34-0410-b5e6-96231b3b80d8