dthelp: fix implicit-function-declaration warnings (the rest)

... at least with regard to the non-generated code.

cde/programs/dthelp/parser/pass1/parser/scan.c

@@ -47,6 +47,8 @@ This product and information is proprietary of Tandem Computers Incorporated.
 #include "entity2.h"
 #include "sref.h"
 
+void m_mberr1(char *text, const char *arg);
+
 /* Actually read a character from an input stream */
 int m_actgetc(void)
   {