Adopt C99 <stdbool.h>'s true/false.

This commit includes <stdbool.h> from defs.h and deletes my
traditional definitions of TRUE and FALSE, but other than that, it's a
100% mechanical search-and-replace transforming all uses of TRUE and
FALSE into the C99-standardised lowercase spellings.

No actual types are changed in this commit; that will come next. This
is just getting the noise out of the way, so that subsequent commits
can have a higher proportion of signal.

contrib/cygtermd/telnet.c

@@ -5,6 +5,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <string.h>
 
 #include "sel.h"
@@ -12,13 +13,6 @@
 #include "malloc.h"
 #include "pty.h"
 
-#ifndef FALSE
-#define FALSE 0
-#endif
-#ifndef TRUE
-#define TRUE 1
-#endif
-
 #define	IAC	255		       /* interpret as command: */
 #define	DONT	254		       /* you are not to use option */
 #define	DO	253		       /* please, you use option */