Add missing long double functions to Cygwin

This patch adds the long double functions missing in newlib to Cygwin.
Apart from some self-written additions (exp10l, finite{f,l}, isinf{f,l},
isnan{f,l}, pow10l) the files are taken from the Mingw-w64 math lib.
Minor changes were required, e.g. substitue _WIN64 with __x86_64__ and
fixing __FLT_RPT_DOMAIN/__FLT_RPT_ERANGE for Cygwin.

Cygwin:
	* math: New subdir with math functions.
	* Makefile.in (VPATH): Add math subdir.
	(MATH_OFILES): List of object files collected from building files in
	math subdir.
	(DLL_OFILES): Add $(MATH_OFILES).
	${CURDIR}/libm.a: Add $(MATH_OFILES) to build.
	* common.din: Add new functions from math subdir.
	* i686.din: Align to new math subdir.  Remove functions now commonly
	available.
	* x86_64.din: Ditto.
	* math.h: math.h wrapper to define mingw structs used in some files in
	math subdir.
	* include/cygwin/version.h: Bump API minor version.

newlib:
	* libc/include/complex.h: Add prototypes for complex long double
	functions.  Only define for Cygwin.
	* libc/include/math.h: Additionally enable prototypes of long double
	functions for Cygwin.  Add Cygwin-only prototypes for dreml, sincosl,
	exp10l and pow10l.  Explain why we don't add them to newlib.
	* libc/include/tgmath.h: Enable long double handling on Cygwin.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/math/ilogbl.S

@@ -0,0 +1,65 @@
+/**
+ * This file has no copyright assigned and is placed in the Public Domain.
+ * This file is part of the mingw-w64 runtime package.
+ * No warranty is given; refer to the file DISCLAIMER.PD within this package.
+ */
+#include <_mingw_mac.h>
+
+	.file	"ilogbl.S"
+	.text
+#ifdef __x86_64__
+	.align 8
+#else
+	.align 4
+#endif
+.globl __MINGW_USYMBOL(ilogbl)
+	.def	__MINGW_USYMBOL(ilogbl);	.scl	2;	.type	32;	.endef
+__MINGW_USYMBOL(ilogbl):
+#ifdef __x86_64__
+	fldt	(%rcx)
+	fxam			/* Is NaN or +-Inf?  */
+	fstsw   %ax
+	movb    $0x45, %dh
+	andb    %ah, %dh
+	cmpb    $0x05, %dh
+	je      1f		/* Is +-Inf, jump.  */
+
+	fxtract
+	pushq	%rax
+	fstp	%st
+
+	fistpl	(%rsp)
+	fwait
+	popq	%rax
+
+	ret
+
+1:	fstp	%st
+	movl	$0x7fffffff, %eax
+	ret
+#else
+	fldt	4(%esp)
+/* I added the following ugly construct because ilogb(+-Inf) is
+   required to return INT_MAX in ISO C99.
+   -- jakub@redhat.com.  */
+	fxam			/* Is NaN or +-Inf?  */
+	fstsw   %ax
+	movb    $0x45, %dh
+	andb    %ah, %dh
+	cmpb    $0x05, %dh
+	je      1f		/* Is +-Inf, jump.  */
+
+	fxtract
+	pushl	%eax
+	fstp	%st
+
+	fistpl	(%esp)
+	fwait
+	popl	%eax
+
+	ret
+
+1:	fstp	%st
+	movl	$0x7fffffff, %eax
+	ret
+#endif