luajit: out-of-bounds read because __gc handler frame traversal is mishandled (CVE-2020-15890 )

LuaJit through 2.1.0-beta3 has an out-of-bounds read because __gc handler frame traversal is mishandled.

References:

• https://github.com/LuaJIT/LuaJIT/issues/601
• https://nvd.nist.gov/vuln/detail/CVE-2020-15890

Affected branches:

• master
• 3.12-stable
• 3.11-stable
• 3.10-stable
• 3.9-stable