Minor Lua fixes.

[jmattsson]

• [x] This PR is for the dev branch rather than for the release branch.
• [x] This PR is compliant with the other contributing guidelines as well (if not, please describe why).
• [x] I have thoroughly tested my contribution*.
• [n/a] The code changes are reflected in the documentation at docs/*.

Issues discovered over on the dev-esp32-idf4 branch while getting the 5.1+5.3 support across to that branch.

• Off by one error in loadLFS, leading to slight memory leak and potential corruption.

• Insufficient return value check in loadLFS, where uzlib may return one of two success conditions, one of which would result in an out-of-bounds access and related pain.

• One case of a side effect within a lua_assert(), leading to silently broken LFS image handling when compiling without asserts enabled, the issue showing up as module names being shuffled around.

• Incorrect encoding of TValues in LFS when 64bit numbers in use.

*) predominantly tested on ESP32

[marcelstoer]

Merge to give it some exposure...