buildroot

lua-bit32: new package

This package is needed to make luaposix work.

The upstream name is just "bit32", but the luarocks infra doesn't
support an upstream name different from the Buildroot name. We therefore
have to explicitly set all variables and we need custom extract
commands.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
[Thomas:
 - add entry to DEVELOPERS file
 - remove useless "depends on BR2_PACKAGE_HAS_LUAINTERPRETER" in
   Config.in file.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>