Since systems that omit strtoumax() will likely omit strtomax() too, and
likewise for strtoull() and strtoll(), we arrange for the make variables
NO_STRTOUMAX and NO_STRTOULL to cover both the signed and unsigned
functions, and define compatibility implementations for them.
Signed-off-by: Nick Alcock <nix@esperi.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>