msvc: Fix build by adding missing INTMAX_MAX define

msvc: Fix build by adding missing INTMAX_MAX define

Commit c03c831 (do not depend on signed integer overflow,
05-10-2010) provokes an msvc build failure. The cause of the
failure is a missing definition of the INTMAX_MAX constant,
used in the new maximum_signed_value_of_type(a) macro, which
would normally be defined in the C99 <stdint.h> header file.

In order the fix the compilation error, we add an appropriate
definition of the INTMAX_MAX constant, along with INTMAX_MIN
and UINTMAX_MAX, to an msvc compat header file.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Acked-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>