Fix ZEND_SIGNED_MULTIPLY_LONG for AArch64

Register operands are required in this context.

This is a backport of 8c86792
to PHP 5.6. The current code caused incorrect behavior on AArch64
when compiling with clang.

Author: shivammathur

Zend/zend_multiply.h

@@ -62,8 +62,8 @@
 	__asm__("mul %0, %2, %3\n"										\
 		"smulh %1, %2, %3\n"										\
 		"sub %1, %1, %0, asr #63\n"									\
-			: "=X"(__tmpvar), "=X"(usedval)							\
-			: "X"(a), "X"(b));										\
+			: "=&r"(__tmpvar), "=&r"(usedval)						\
+			: "r"(a), "r"(b));										\
 	if (usedval) (dval) = (double) (a) * (double) (b);				\
 	else (lval) = __tmpvar;											\
 } while (0)