Fix detection of floating point assembly instructions. They were

incorrectly detcted as present because gcc was optimising them away.

configure.ac

@@ -113,15 +113,15 @@ AC_TRY_COMPILE([#include <windows.h>],[Sleep(42);],
  [AC_MSG_RESULT(no)])
 
 AC_MSG_CHECKING(for fsin/fcos)
-AC_TRY_COMPILE([],[double x; asm("fsin\n\tfcos":"=t"(x):);],
+AC_TRY_COMPILE([],[double x; asm volatile("fsin\n\tfcos":"=t"(x):);],
  [AC_MSG_RESULT(yes)
-  AC_DEFINE(HAVE_FSIN_FCOS, 1, [Define to 1 if you have the `fsin' and `fcos' operands.])],
+  AC_DEFINE(HAVE_FSIN_FCOS, 1, [Define to 1 if you have the `fsin' and `fcos' instructions.])],
  [AC_MSG_RESULT(no)])
 
 AC_MSG_CHECKING(for fldln2/fxch/fyl2x)
-AC_TRY_COMPILE([],[double x; asm("fldln2; fldln2; fxch; fyl2x":"=t"(x):);],
+AC_TRY_COMPILE([],[double x; asm volatile("fldln2; fldln2; fxch; fyl2x":"=t"(x):);],
  [AC_MSG_RESULT(yes)
-  AC_DEFINE(HAVE_FLDLN2, 1, [Define to 1 if you have the `fldln2' and other floating points operands.])],
+  AC_DEFINE(HAVE_FLDLN2, 1, [Define to 1 if you have the `fldln2' and other floating point instructions.])],
  [AC_MSG_RESULT(no)])
 
 AC_CHECK_HEADERS(zlib.h)