glMLite is not compatible with ocaml 5
```
=== ERROR while compiling glMLite.0.03.53 ====================================#
context 2.2.0~alpha~dev | linux/x86_64 | ocaml-base-compiler.5.0.0 | file:///home/opam/opam-repository
path ~/.opam/5.0/.opam-switch/build/glMLite.0.03.53
command ~/.opam/opam-init/hooks/sandbox.sh build make
exit-code 2
env-file ~/.opam/log/glMLite-7-40c74d.env
output-file ~/.opam/log/glMLite-7-40c74d.out
(cd SRC; make)
make[1]: Entering directory '/home/opam/.opam/5.0/.opam-switch/build/glMLite.0.03.53/SRC'
if [ ! -d enums ]; then mkdir enums ; fi
ocamlc -c -g -o xmlm.cmi xmlm.mli
ocamlopt -c -g -o xmlm.cmx xmlm.ml
File "xmlm.ml", line 1128, characters 18-34:
1128 | let lowercase = String.lowercase
^^^^^^^^^^^^^^^^
Error: Unbound value String.lowercase
make[1]: *** [Makefile.enums:58: xmlm.cmx] Error 2
make[1]: Leaving directory '/home/opam/.opam/5.0/.opam-switch/build/glMLite.0.03.53/SRC'
make: *** [Makefile:32: all] Error 2
```
Signed-off-by: Marcello Seri <marcello.seri@gmail.com>