[inline-asm]No error for conflict between inputs\outputs and clobber list

According to extended asm syntax, a case where the clobber list includes a variable from the inputs or outputs should be an error - conflict.
for example:

const long double a = 0.0;
int main()
{

char b;
double t1 = a;
__asm__ ("fucompp": "=a" (b) : "u" (t1), "t" (t1) : "cc", "st", "st(1)");

return 0;
}

This should conflict with the output - t1 which is st, and st which is st aswell.
The patch fixes it.

Commit on behald of Ziv Izhar.

Differential Revision: https://reviews.llvm.org/D15075

llvm-svn: 290539