Enable LUA_USE_POSIX, fix tmpnam warning on macOS.

Fixes #63

On macOS, we want to use `mkstemp` rather than `tmpnam`. Enable
POSIX support in Lua to fix that (and some other things). Since
POSIX support also enables the flag for POPEN, we no longer need
to do that directly for Linux.

Resolves #109

Fixes #100

Filenames that match either the single pattern provided by
`config.ignore_files`, or any pattern in a table of patterns, will be ignored
when lite is filling the `core.project_files` table

Resolves #77
Resolves #102

Fixed various issues in exec:replace

Fixes #97

This, along with the earlier rencache changes should resolve #64

Resolves #71
Resolves #59

Resolves #86
Resolves #87

Resolves #80

`autocomplete.add()` can now be used to add additional auto complete suggestions
with descriptions

Build fix

Fixing trimwhitespace plugin bug

Update language_js.lua