win: math.h: fix fpclassify/signbit/etc - use C instead of broken asm

The asm code cannot currently be used with tcc since tcc doesn't support 't'
constraint.

Use inline C implementation instead, place it win32/include/tcc/tcc_libm.h, and
include it from win32/include/math.h.

Since fpclassify now works, it also fixes few other macros which depend on it.
Implicitly fixed: isfinite, isinf, isnan, isnormal.

The implementations were taken from musl-libc rs-1.0 (MIT license).

musl-libc: http://git.musl-libc.org/cgit/musl/tree/src/math?h=rs-1.0
license:   http://git.musl-libc.org/cgit/musl/tree/COPYRIGHT?h=rs-1.0

win32/include/tcc/tcc_libm.h

@@ -0,0 +1,88 @@
+#ifndef _TCC_LIBM_H_
+#define _TCC_LIBM_H_
+
+#include "../include/math.h"
+
+/* TCC uses 8 bytes for double and long double, so effectively the l variants
+ * are never used. For now, they just run the normal (double) variant.
+ */
+
+/*
+ * most of the code in this file is taken from MUSL rs-1.0 (MIT license)
+ * - musl-libc: http://git.musl-libc.org/cgit/musl/tree/src/math?h=rs-1.0
+ * - License:   http://git.musl-libc.org/cgit/musl/tree/COPYRIGHT?h=rs-1.0
+ */
+
+/*******************************************************************************
+  Start of code based on MUSL
+*******************************************************************************/
+/*
+musl as a whole is licensed under the following standard MIT license:
+
+----------------------------------------------------------------------
+Copyright <20> 2005-2014 Rich Felker, et al.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+----------------------------------------------------------------------
+*/
+
+/* fpclassify */
+
+__CRT_INLINE int __cdecl __fpclassify (double x) {
+  union {double f; uint64_t i;} u = {x};
+  int e = u.i>>52 & 0x7ff;
+  if (!e) return u.i<<1 ? FP_SUBNORMAL : FP_ZERO;
+  if (e==0x7ff) return u.i<<12 ? FP_NAN : FP_INFINITE;
+  return FP_NORMAL;
+}
+
+__CRT_INLINE int __cdecl __fpclassifyf (float x) {
+  union {float f; uint32_t i;} u = {x};
+  int e = u.i>>23 & 0xff;
+  if (!e) return u.i<<1 ? FP_SUBNORMAL : FP_ZERO;
+  if (e==0xff) return u.i<<9 ? FP_NAN : FP_INFINITE;
+  return FP_NORMAL;
+}
+
+__CRT_INLINE int __cdecl __fpclassifyl (long double x) {
+  return __fpclassify(x);
+}
+
+/* signbit */
+
+__CRT_INLINE int __cdecl __signbit (double x) {
+  union {double d; uint64_t i;} y = { x };
+  return y.i>>63;
+}
+
+__CRT_INLINE int __cdecl __signbitf (float x) {
+  union {float f; uint32_t i; } y = { x };
+  return y.i>>31;
+}
+
+__CRT_INLINE int __cdecl __signbitl (long double x) {
+  return __signbit(x);
+}
+
+/*******************************************************************************
+  End of code based on MUSL
+*******************************************************************************/
+
+#endif /* _TCC_LIBM_H_ */