On the msvc build, the tests t0401-parse and t0501-walk both
crash with a runtime error (ACCESS_VIOLATION). This is caused
by writing to un-allocated memory due to an under-allocation
of a git_revpool_table data structure.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Andreas Ericsson <ae@op5.se>