SHELLERS for SYSCF, MacOS 10.5 hints file (trunk only)

Add SHELLERS - people allowed to use ! command with same syntax as WIZARDS.
Add new hints file for 10.5, since the rules and commands for groups changed
(new commands introduced in 10.4, old ones removed in 10.5; creating a new
user under 10.4 gave you a matching group, in 10.5 it doesn't).  Also move
shared build into roughly right place in file system when being installed
for root - don't use ~root.
Makefile.top - don't remove ./-p unless it exists (that's always annoyed me).
fix error invoking macosx.sh

include/unixconf.h

@@ -279,7 +279,9 @@
 #endif
 #define tgetch getchar
 
-#define SHELL		/* do not delete the '!' command */
+#ifndef NOSHELL
+# define SHELL		/* do not delete the '!' command */
+#endif
 
 #include "system.h"