update-all-config: convert from .sh to .pl
The POSIX sh version is very POSIXy and also VERY SLOW.
The shell is just not capable of doing the needed checks
efficiently -- lots and lots of processes get spawned.
The new perl version runs much, much faster. It still
spawns out for find results (there doesn't seem to be
an obviously faster way to get those), but now all the
mode and group checking and changing is fully internal
and so is the config checking (although changing still
spawns git config).
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>