lua: bump version to 5.1.5

[thomas.petazzoni@free-electrons.com: rewrote the patch, which was
corrupted in the original submission. Used quilt to refresh the Lua
patches, so that the version numbers are no longer present in the file
names]

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>