Added a commented out -Wmissing-prototypes to CFLAGS.

It is commented out to not break builds with 3rd party modules.

auto/cc/gcc

diff --git a/auto/cc/gcc b/auto/cc/gcc
index de666a3..1740a5f 100644
--- a/auto/cc/gcc
+++ b/auto/cc/gcc
@@ -149,6 +149,7 @@
 CFLAGS="$CFLAGS -Wall -Wpointer-arith"
 #CFLAGS="$CFLAGS -Wconversion"
 #CFLAGS="$CFLAGS -Winline"
+#CFLAGS="$CFLAGS -Wmissing-prototypes"
 
 
 case "$NGX_GCC_VER" in