Resolve many build warnings

This patch fixes many warnings from the beginning of the build up to
and including the depend stage. Nearly all warnings should be gone
even with -Wall.

cde/programs/dthelp/parser/canon1/build/proto.h

@@ -330,7 +330,7 @@ LOGICAL litproc(
 #endif
   ) ;
 
-void main(
+int main(
 #if defined(M_PROTO)
   int argc, char **argv
 #endif