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/exp2.S

@@ -0,0 +1,94 @@
+/**
+ * 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	"exp2.S"
+	.text
+#ifdef __x86_64__
+	.align 8
+#else
+	.align 4
+#endif
+.globl __MINGW_USYMBOL(exp2)
+	.def	__MINGW_USYMBOL(exp2);	.scl	2;	.type	32;	.endef
+__MINGW_USYMBOL(exp2):
+#ifdef __x86_64__
+	subq	$24, %rsp
+	movsd	%xmm0,(%rsp)
+	fldl	(%rsp)
+	fxam				/* Is NaN or +-Inf?  */
+	fstsw	%ax
+	movb	$0x45, %dh
+	andb	%ah, %dh
+	cmpb	$0x05, %dh
+	je	1f			/* Is +-Inf, jump.  */
+	fld	%st
+  	subq $8, %rsp /* int(x) */
+    	fnstcw 4(%rsp)
+    	movzwl 4(%rsp), %eax
+    	orb $12, %ah
+    	movw %ax, (%rsp)
+    	fldcw (%rsp)
+    	frndint
+    	fldcw 4(%rsp)
+    	addq $8, %rsp
+	fsubr	%st,%st(1)		/* fract(x) */
+	fxch
+	f2xm1				/* 2^(fract(x)) - 1 */
+	fld1
+	faddp				/* 2^(fract(x)) */
+	fscale				/* e^x */
+	fstp	%st(1)
+	fstpl	(%rsp)
+	movsd	(%rsp),%xmm0
+	addq	$24, %rsp
+	ret
+
+1:	testl	$0x200, %eax		/* Test sign.  */
+	jz	2f			/* If positive, jump.  */
+	fstp	%st
+	fldz				/* Set result to 0.  */
+2:	fstpl	(%rsp)
+	movsd	(%rsp),%xmm0
+	addq	$24,%rsp
+	ret
+#else
+	fldl	4(%esp)
+/* I added the following ugly construct because exp(+-Inf) resulted
+   in NaN.  The ugliness results from the bright minds at Intel.
+   For the i686 the code can be written better.
+   -- drepper@cygnus.com.  */
+	fxam				/* Is NaN or +-Inf?  */
+	fstsw	%ax
+	movb	$0x45, %dh
+	andb	%ah, %dh
+	cmpb	$0x05, %dh
+	je	1f			/* Is +-Inf, jump.  */
+	fld	%st
+	subl $8, %esp /* int(x) */
+	fnstcw 4(%esp)
+	movzwl 4(%esp), %eax
+	orb $12, %ah
+	movw %ax, (%esp)
+	fldcw (%esp)
+	frndint
+	fldcw 4(%esp)
+	addl $8, %esp
+	fsubr	%st,%st(1)		/* fract(x) */
+	fxch
+	f2xm1				/* 2^(fract(x)) - 1 */
+	fld1
+	faddp				/* 2^(fract(x)) */
+	fscale				/* e^x */
+	fstp	%st(1)
+	ret
+
+1:	testl	$0x200, %eax		/* Test sign.  */
+	jz	2f			/* If positive, jump.  */
+	fstp	%st
+	fldz				/* Set result to 0.  */
+2:	ret
+#endif