Merge pull request #1086 from sunxb10/master

Added new resources in zh.md (Chinese)
Added The GNU C Programming Tutorial
Merge pull request #1087 from bit4bit/master

Added The GNU C Programming Tutorial
Add Programación de videojueos con SDL to spanish books
Merge pull request #1088 from bit4bit/master

Add Programación de videojueos con SDL to spanish books
Merge pull request #2 from vhf/master

sync with vhf:master