Removed OpenAL and GLFW3 dependencies on building.
Reviewed platforms and flags

Inspired by #504.
Instead of requiring the user to do PLATFORM_ANDROID #ifdefery,
have the android_main entry point exported by raylib and call
the user-defined main. This way many games could (in theory)
run unmodified on Android and elsewhere.

This is untested!

Supported UTF8 range equivalent to [128..255] (80h..FFh)
Exposed and renamed text function GetGlyphIndex()
Renamed spriteFont parameter name to simply font
Small security check on transmission mission ending screen

Support string replacing to generate newspaper headline
ISSUE: UTF8 characters not supported when drawing to Image

Game developed in the GGJ18, it has some bugs and ending screen is
incomplete... I'll try to keep working a bit more on it.

They were disabled because they failed to build,
but this patch set fixes the build on Linux and macOS.

This doesn't apply to the AppVeyor build on Windows yet;
it currently fails at linking with OpenAL.

Now it works! :)

Some people might find this handly

Now works in WEB!

- Removed raylib_demo (outdated)
- Removed some old examples

Related to UpdateMusicStream(), in stb_vorbis

Detected a VERY weird code behaviour... :(

Render wave in a render target
Implemented combo system
Removed big useless audio (fxWave)

Updated to new audio system

It's more educational to go through new material system, so, I decide to
remove this function to avoid students confusion...