Kill most warnings in lib/DtTerm.

Mostly missing headers, explicit parentheses and new prototypes.

Some Caveats:
* I haven't compile-tested the SVR4 getpty file, it might need another tweak
* There were operator precedence bugs in TermPrimCursor.c and TermPrimRender.c
  (^ vs. !=).  This might change behaviour, but at least I haven't experienced
  any crashes ...
* This adds a little more dependencies for include ordering, but unless we
  want to play the "headers that include headers that include headers..." game,
  this is unavoidable.

cde/lib/DtTerm/TermPrim/TermPrimBufferP.h

@@ -174,6 +174,29 @@ typedef struct _TermBufferRec
     TermBufferPart term_buffer;
 } TermBufferRec;
 
+extern
+short
+_DtTermPrimBufferInsertWc
+(
+    const TermBuffer  tb,
+    const short       row,
+    const short       col,
+          wchar_t    *newChars,
+          short       numChars,
+          Boolean     insertFlag,
+          termChar  **returnChars,
+          short      *returnLength
+);
+
+extern
+Boolean
+_DtTermPrimBufferClearLineWc
+(
+    const TermBuffer  tb,
+    const short       row,
+          short       newWidth
+);
+
 #ifdef	__cplusplus
 } /* close scope of 'extern "C"'... */
 #endif	/* __cplusplus */