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/catan.c

@@ -0,0 +1,49 @@
+/* catan.c */
+
+/*
+   Contributed by Danny Smith
+   2003-10-17
+
+   FIXME: This needs some serious numerical analysis.
+*/
+
+#include <math.h>
+#include <complex.h>
+#include <errno.h>
+
+/* catan (z) = -I/2 * clog ((I + z) / (I - z)) */ 
+
+double complex 
+catan (double complex Z)
+{
+  double complex Res;
+  double complex Tmp;
+  double x = __real__ Z;
+  double y = __imag__ Z;
+
+  if ( x == 0.0 && (1.0 - fabs (y)) == 0.0)
+    {
+      errno = ERANGE;
+      __real__ Res = HUGE_VAL;
+      __imag__ Res = HUGE_VAL;
+    }
+   else if (isinf (_hypot (x, y)))
+   {
+     __real__ Res = (x > 0 ? M_PI_2 : -M_PI_2);
+     __imag__ Res = 0.0;
+   }
+  else
+    {
+      __real__ Tmp = - x; 
+      __imag__ Tmp = 1.0 - y;
+
+      __real__ Res = x; 
+      __imag__ Res = y + 1.0;
+
+      Tmp = clog (Res/Tmp);	
+      __real__ Res  = - 0.5 * __imag__ Tmp;
+      __imag__ Res =  0.5 * __real__ Tmp;
+    }
+
+   return Res; 
+}