[PowerPC64LE] Fix Lua 5.2 runtime issue

[bdragon]

Summary

Lua 5.2 (but not earlier or later versions) have a powerpc platform detection check.

This check was not using the preferred define __powerpc__ so fails to trigger on gcc.

It also assumes that all of powerpc is big-endian.

Check a more universal preprocessor define, and add support for the upcoming FreeBSD PowerPC64LE.

Submitted by: Daniel Kolesa <[e-mail]>

Test Plan

Before:

root@fledgling:~ # uname -p
powerpc64le
root@fledgling:~ # lua52
lua52: bad conversion number->int; must recompile Lua with proper settings
`

After:

root@fledgling:/fluffy/ports-LE/lang/lua52 # lua52
Lua 5.2.4  Copyright (C) 1994-2015 Lua.org, PUC-Rio
>

[luporl]

Looks good to me.