Mention the issues about the rate control if frame skipping is disabled

As requested by Volvet in the review of the frame skipping option.
Merge pull request #173 from mstorsjo/readme-rc-issue

Mention the issues about the rate control if frame skipping is disabled
Remove the __NO_CTYPE define

Nothing within the project uses it, and it's not necessary to
build the project either, tested on both linux and mingw.
Fix building of macos bundle loading code on 64 bit
Remove an unused function

This function contains a lot of platform specific constants
whose use is unknown.
Remove system header/define hackery in welsenc.cpp

There doesn't seem to be any actual need for this, building
on linux still works just fine.
Merge pull request #175 from mstorsjo/remove-unused-define

Remove the __NO_CTYPE define
Merge pull request #177 from mstorsjo/remove-unused-function

Remove an unused function
Merge pull request #178 from mstorsjo/remove-system-header-hackery

Remove system header/define hackery in welsenc.cpp
Merge pull request #179 from mstorsjo/fix-bundleloader-64bit

Fix building of macos bundle loading code on 64 bit
Merge remote-tracking branch 'upstream/master' into travis.osx