configure: Check MSVC defines for identifying hardfloat

This macro identifies whether VFPv3 is available; MSVC defaults
to hardfloat (except for older MSVC versions for CE, targeting
ARMv4).
Signed-off-by: NMartin Storsjö <martin@martin.st>

configure

@@ -4001,6 +4001,8 @@ elif enabled arm; then
 
     if     check_cpp_condition stddef.h "defined __ARM_PCS_VFP"; then
         enable vfp_args
+    elif check_cpp_condition stddef.h "defined _M_ARM_FP && _M_ARM_FP >= 30"; then
+        enable vfp_args
     elif ! check_cpp_condition stddef.h "defined __ARM_PCS || defined __SOFTFP__"; then
         case "${cross_prefix:-$cc}" in
             *hardfloat*)         enable vfp_args;   fpabi=vfp ;;