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.
