fix: avoid int overflow in rlimit.c
(cherry picked from commit 6ace3051babf6d4083ff3aabc1f7e6885356e220)

Signed-off-by: Andreas Steenpass <steenpass@mathematik.uni-kl.de>
Merge pull request #421 from steenpass/rlimit_sw

fix: avoid int overflow in rlimit.c