Cleanup of includes and related changes based on include-what-you-use diagnostics (#436)

Remove unused #define PERCENT_OF_SCREEN in MyWindow.h
Move structures for dir.c to dirdefs.h where they are used
Resolve S_CHAR vs S_CHARACTER in favor of S_CHARACTER and cleanup #defines
Fix  = vs == bug in FSDEBUG code in dir.c
Eliminate duplicate/unused constant definitions in gcr.c
Declare static internal function bytecmp in mkatom.c
Update many source and include files to include headers for what they use

inc/stack.h

@@ -8,8 +8,11 @@
 /*	Manufactured in the United States of America.			*/
 /*									*/
 /************************************************************************/
+#include "version.h"  /* for BIGVM, UNSIGNED */
+#include "adr68k.h"   /* for LADDR_from_68k */
+#include "address.h"  /* for LOLOC */
+#include "commondefs.h" /* for error */
 #include "lispemul.h" /* for LispPTR, DLword, FRAMESIZE, DLWORDSPER_CELL */
-#include "version.h" /* for BIGVM, UNSIGNED */
 
 /* ContextSW frame number */
 #define CurrentFXP 0
@@ -383,6 +386,7 @@ typedef struct stackp {
 #ifdef STACKCHECK
 
 #include <stdio.h>
+#include "testtooldefs.h"
 
 #define S_CHECK(condition, msg)                          \
   {                                                      \