changed C source to use C booleans with backward compatibility

Fix "Under source code control" date for new version.h file.

Sorted the order of symbols printed by "make env".

Test if <stdbool.h> exists and set HAVE_STDBOOL_H accordingly
in have_stdbool.h.  Added HAVE_STDBOOL_H to allow one to force
this value.

Added "bool.h" include file to support use of boolean symbols,
true and false for pre-c99 C compilers.  The "bool.h" include
file defines TRUE as true, FALSE as false, and BOOL as bool:
for backward compatibility.

The sign in a ZVALUE is now of type SIGN, whcih is either
SB32 when CALC2_COMPAT is defined, or a bool.

Replaced in C source, TRUE with true, FALSE with false, and
BOOL with bool.

block.h

@@ -1,7 +1,7 @@
 /*
  * block - fixed, dynamic, fifo and circular memory blocks
  *
- * Copyright (C) 1999-2007,2014,2021  Landon Curt Noll and Ernest Bowen
+ * Copyright (C) 1999-2007,2014,2021,2023  Landon Curt Noll and Ernest Bowen
  *
  * Primary author:  Landon Curt Noll
  *
@@ -122,7 +122,7 @@
  *		number of octets of a block to print, 0 means all
  *
  *	config("blkverbose", boolean)
- *		TRUE => print all lines, FALSE => skip dup lines
+ *		true => print all lines, false => skip dup lines
  *
  *	config("blkbase", "base")
  *		output block base = { "hex", "octal", "char", "binary", "raw" }