Clean up compiler warnings:

* bcache.h, bcache.c, c-valprint.c, coffread.c, stabsread.c,
	stack.c, valprint.c: Change variables to unsigned.
	* bcache.c: Rearrange to avoid warnings about variables not being set.
	* c-lang.c, ch-lang.c, f-lang.c, m2-lang.c: Include valprint.h
	rather than declaring print_max and repeat_count_threashold
	ourselves (incorrectly).
	* valprint.h: Do declare repeat_count_threashold.
	* ch-exp.c: Use default case for internal error.
	* findvar.c: Don't omit argument type.
	* symtab.c: Remove unused variable.

gdb/stack.c

@@ -1204,7 +1204,7 @@ backtrace_command (arg, from_tty)
       argc = 0;
       for (i = 0; (argv[i] != (char *) NULL); i++)
 	{
-	  int j;
+	  unsigned int j;
 
 	  for (j = 0; (j < strlen (argv[i])); j++)
 	    argv[i][j] = tolower (argv[i][j]);