TS-2269 regex_remap plugin does not deal with empty path's properly.

This is a problem when the request URL path is just '/', which inside
of ATS is an emptry string.

Review: leif
Added TS-2269.
TS-2254 On ARM arch, ink_atomic_increment returns wrong value

It should return the old value, before the increment. This is
consistent with how the other ink_atomic_increment implementation
works.

Review: leif
Added TS-2254.