SYSCF bits

(This covers some thing that Pat found and some things I found while working
on those.)
Unscramble duplicate use of GREPPATH and GDBPATH symbols.
Add some more info to config.h.
Make missing SYSCF_FILE a fatal error.
Make a parse error in SYSCF_FILE a fatal error.
Rename PANICTRACE_GLIBC (et al) to PANICTRACE_LIBC (et al) since FreeBSD
 and Mac OS X (at least) also implement the needed API.
Allow SYSCF_FILE to be unreadable by the user (for setgid installs).
If SYSCF, do NOT fall back to the compiled in WIZARD account.
Put WIZARD into sysopt and remove special cases in authorize_wizard_mode().

sys/unix/unixunix.c

@@ -371,3 +371,18 @@ gid_t
 }
 
 #endif	/* GETRES_SUPPORT */
+
+/* XXX should be ifdef PANICTRACE_GDB, but there's no such symbol yet */
+#ifdef PANICTRACE
+boolean
+file_exists(const char *path){
+	/* Just see if it's there - trying to figure out if we can actually
+	 * execute it in all cases is too hard - we really just want to
+	 * catch typos in SYSCF. */
+	struct stat sb;
+	if(stat(path, &sb)){
+		return FALSE;
+	}
+	return TRUE;
+}
+#endif