Description: make sure C99 features are enabled in GCC's C99 mode
Bug-Dyson: https://www.osdyson.org/issues/191
Index: libc/usr/src/head/math.h
===================================================================
--- libc.orig/usr/src/head/math.h
+++ libc/usr/src/head/math.h
@@ -29,6 +29,8 @@
 #ifndef _MATH_H
 #define	_MATH_H
 
+#include <features.h>
+
 #include <iso/math_iso.h>
 #include <iso/math_c99.h>
 #include <ieeefp.h>