build: don't install some files if only libmpv is built

encoding-profiles.conf can be used by libmpv, but it won't load it
from this path by default, so exclude it as well.

Fixes #1293.
TOOLS/lua: add script that pauses playback when minimizing the window

Uses functionality that was added a month ago for exactly this purpose.

Fixes #1237.
lua: add a function that formats Lua values as strings

Yep, Lua is so crappy that the stdlib doesn't provide anything like
this.

Repurposes the undocumented mp.format_table() function and moves it to
mp.utils.
vo_opengl: disable fancy-downscaling for anamorphic video

Includes some arbitrary minor refactoring.
vo_opengl: enable fancy-downscaling by default for opengl-hq