Add ISO C99 complex support for doubles.

* include/complex.h: New file.
	* mingwex/complex: New directory.
	* mingwex/complex/cabs.c: New file.
	* mingwex/complex/cacos.c: New file.
	* mingwex/complex/cacosh.c: New file.
	* mingwex/complex/casin.c: New file.
	* mingwex/complex/casinh.c: New file.
	* mingwex/complex/catan.c: New file.
	* mingwex/complex/catanh.c: New file.
	* mingwex/complex/ccos.c: New file.
	* mingwex/complex/ccosh.c: New file.
	* mingwex/complex/cexp.c: New file.
	* mingwex/complex/cimag.c: New file.
	* mingwex/complex/clog.c: New file.
	* mingwex/complex/cpow.c: New file.
	* mingwex/complex/cproj.c: New file.
	* mingwex/complex/creal.c: New file.
	* mingwex/complex/csin.c: New file.
	* mingwex/complex/csinh.c: New file.
	* mingwex/complex/csqrt.c: New file.
	* mingwex/complex/ctan.c: New file.
	* mingwex/complex/ctanh.c: New file.
	* mingwex/Makefile.in (COMPLEX_DISTFILES): New list of
	files.
	(dist): Use it.
	(COMPLEX_OBJS): New list of objects.
	(LIB_OBJS): Include it in the library.

winsup/mingw/mingwex/complex/cacos.c

@@ -0,0 +1,82 @@
+/*
+   cacos.c
+   Contributed by Danny Smith
+   2003-10-20
+*/
+
+#include <math.h>
+#include <complex.h>
+
+#if 0
+/* cacos (Z) = -I * clog(Z + I * csqrt(1 - Z * Z)) */
+
+double complex cacos (double  complex Z)
+{
+  double complex Res;
+  double x, y;
+
+  x = __real__ Z;
+  y = __imag__ Z;
+
+  if (y == 0.0)
+    {
+      __real__ Res = acos (x);
+      __imag__ Res = 0.0;
+    }
+
+  else
+    {
+      double complex ZZ;
+      /* Z * Z = ((x - y) * (x + y)) + (2.0 * x * y) * I */
+      /* caculate 1 - Z * Z */
+      __real__ ZZ = 1.0 - (x - y) * (x + y);
+      __imag__ ZZ = -2.0 * x * y;
+
+       
+       Res = csqrt(ZZ);
+
+      /* calculate ZZ + I * sqrt (ZZ) */
+    
+      __real__ ZZ = x - __imag__ Res;
+      __imag__ ZZ = y + __real__ Res;
+       
+      ZZ = clog(ZZ);
+
+      /* mult by -I */
+
+      __real__ Res  =  __imag__ ZZ;
+      __imag__ Res = - __real__ ZZ;
+    }
+  return Res;
+}
+
+#else
+
+/* cacos ( Z ) =  pi/2 - casin ( Z ) */
+
+double complex cacos (double complex Z)
+{
+  double complex Res  = casin (Z);
+  __real__ Res = M_PI_2 - __real__ Res;
+  __imag__ Res = - __imag__ Res;
+  return Res;
+}
+#endif
+
+#if 0
+#include <stdio.h>
+int main()
+{
+  double z;
+  double complex bar = 0.7 + 1.2  * I;
+  double complex foo = cacos (bar);
+
+  printf ("%.16e\t%.16e\n", __real__ foo, __imag__ foo);
+
+  foo = cacos (bar);
+  printf ("%.16e\t%.16e\n", __real__ foo, __imag__ foo);
+
+  return 1;
+}
+#endif
+