Merge branch 'functions' of https://github.com/VECcom/Tetris into interface

Conflicts:
	functions.c
Merge branch 'master' of https://github.com/VECcom/Tetris into interface

Conflicts:
	functions.c
added SDL
TODO: Spawn Bug, RGB To HSV Bug
Stylechanges and Bugfixes
fix SEGV at the end of the game
Fixed SIGSEV error
Small changes
Merge branch 'functions' of https://github.com/VECcom/Tetris into interface

Conflicts:
	Makefile
	functions.c
	interface.c
	main.c
modified position calculating and added interface option
SDL sometimes caused SIGSEV in glClearColor() and ajusted postion of the field
started with creating of the interface
Prototype of Interface and fixed several bugs
small codechanges
...
Text + OpenGL sucks
Fixed false exiting and added a pause function ... key p to pause and key c to continue
Small changes regarding Initialisation and paused Message
added Messagesystem shows chain and Tetris
Enabled Double Buffering and finished the menu