update stb_truetype

Fixes bug where text would be drawn/cached wrongly if more than one tab_width
was used in a given frame

Resolves #158
Resolves #103

Resolves #159
Resolves #161

This reverts commit 6a7e214d1cb7ecdd292dd2b17c17f2504904db4e.

Fix for keypad enter issue

Don't tell the system to disable compositing under X11

Fixes #123

The value should not be updated if the current first_invalid_line is less than
the new invalid line index

the current-working-directory is now set at the start of `core.init` after the
absolute path for all filename arguments have been resolved

As the window isn't created until the first frame is drawn this is required to
assure the window is ever shown without relying on the assumption that some
other part of the program would have set this to true

Enable LUA_USE_POSIX, fix tmpnam warning on macOS.