Add incomplet long double math support to libmingwex.a

winsup/mingw/mingwex/math/signbitf.c

@@ -0,0 +1,10 @@
+#define __FP_SIGNBIT  0x0200
+
+int __signbitf (float x) {
+  unsigned short sw;
+  __asm__ ("fxam; fstsw %%ax;"
+	   : "=a" (sw)
+	   : "t" (x) );
+  return sw & __FP_SIGNBIT;
+}
+int __attribute__ ((alias ("__signbitf"))) signbitf (float);