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

src/timer.c

@@ -60,6 +60,7 @@ extern int ether_fd;
 #include "lispmap.h"
 #include "stack.h"
 #include "dbprint.h"
+#include "miscstat.h"
 
 #include "timerdefs.h"
 #include "commondefs.h"