add ounit based compat layer for fort

fort is not available on opam so it's best not to depend on it
remove unused env module

the useful parts of it were moved to fort_unit
convert emacs tests to fort_unit
convert test_perl to fort_unit
convert test_re to fort_unit
convert test_str tests to fort_unit

these are failing currently as expected
update oasis for new tests

* fort_unit compat layer for old tests
* add test/executable sections for all tests
* str test section commented out b/c it's failing
regenerate oasis
use Bytes everwhere it is needed
remove Cset.Map

not used anywhere
Merge pull request #39 from rgrinberg/cset_cleanup

remove Cset.Map
Merge pull request #34 from rgrinberg/revive_old_tests

Revive old tests
regenerate oasis
Merge branch 'c-cube-safe-string-ready'
module Re.Easy with high level search (iterate on all matched substrings), split and replacing functions
add some tests for Re.Easy
fix bug in Easy.replace when ~all:false
add a test case for split
changed the API (remove module Easy, better function names)
split_full implemented