DOCS: convert mpv.io and github links to https

Discovered with:

find . -type f \( -name '*.md' -o -name '*.rst' \)  -exec grep -n 'http://' {} +

All links to mpv.io or github.com/mpv-player that were http were
converted to https.

DOCS/man/libmpv.rst

@@ -10,9 +10,9 @@ Since libmpv merely allows access to underlying mechanisms that can control
 mpv, further documentation is spread over a few places:
 
 - https://github.com/mpv-player/mpv/blob/master/libmpv/client.h
-- http://mpv.io/manual/master/#options
-- http://mpv.io/manual/master/#list-of-input-commands
-- http://mpv.io/manual/master/#properties
+- https://mpv.io/manual/master/#options
+- https://mpv.io/manual/master/#list-of-input-commands
+- https://mpv.io/manual/master/#properties
 - https://github.com/mpv-player/mpv-examples/tree/master/libmpv
 
 C PLUGINS

DOCS/mplayer-changes.rst

@@ -52,7 +52,7 @@ Input
 * Classic LIRC support was removed. Install remotes as input devices instead.
   This way they will send X11 key events to the mpv window, which can be bound
   using the normal ``input.conf``.
-  Also see: http://github.com/mpv-player/mpv/wiki/IR-remotes
+  Also see: https://github.com/mpv-player/mpv/wiki/IR-remotes
 * Joystick support was removed. It was considered useless and was the cause
   of some problems (e.g. a laptop's accelerator being recognized as joystick).
 * Support for relative seeking by percentage.

README.md

@@ -21,7 +21,7 @@
 
 * [Wiki](https://github.com/mpv-player/mpv/wiki)
 * [FAQ][FAQ]
-* [Manual](http://mpv.io/manual/master/)
+* [Manual](https://mpv.io/manual/master/)
 
 
 ## Overview
@@ -53,7 +53,7 @@ Releases can be found on the [release list][releases].
 
 
 For semi-official builds and third-party packages please see
-[mpv.io/installation](http://mpv.io/installation/).
+[mpv.io/installation](https://mpv.io/installation/).
 
 ## Changelog