add hypot to math.h for X11, its already in libc it just needs the definition.
hypot() wasn't in V7 Unix, but is part of ISO-C (IEEE Std 1003.1-2001).

Reference: /n/sources/patch/applied/ape-hypot
Date: Thu Feb 28 16:55:58 CET 2013
Signed-off-by: steve@quintile.net

--- /386/include/ape/math.h	Thu Feb 28 16:52:35 2013
+++ /386/include/ape/math.h	Thu Feb 28 16:52:31 2013
@@ -15,6 +15,7 @@
 extern double atan(double);
 extern double atan2(double, double);
 extern double cos(double);
+extern double hypot(double, double);
 extern double sin(double);
 extern double tan(double);
 extern double cosh(double);