The new function parses an integeral value that fits in unsigned
long in human readable form, i.e. possibly with unit suffix, e.g.
10k = 10240, etc., from an environment variable. Parsing of
GIT_MMAP_LIMIT and GIT_ALLOC_LIMIT will use it in later patches.
Signed-off-by: Steffen Prohaska <prohaska@zib.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>