Update free-programming-books-pl.md

Added link to opengl course in c++ (http://cpp0x.pl/kursy/Kurs-OpenGL-C++/)
Update free-programming-books-pl.md

Added java course (http://javastart.pl)
Merge pull request #524 from CucumisSativus/patch-1

Update free-programming-books-pl.md
Merge pull request #525 from CucumisSativus/master

Update free-programming-books-pl.md
Update free-programming-books.md
Merge pull request #527 from kracekumar/patch-1

Update free-programming-books.md
Added PHP section to spanish version

Include the PHP section for the spansih reference books, then added the
"Manual de PHP".
Fix the C++ link (free-programming-books-es.md)

The c++ contextual link did not work.
Revert "Fix the C++ link (free-programming-books-es.md)"

This reverts commit aa26bdabe34dd46c4a148a11ac41009bd7d35b25.
Fix the C++ link (free-programming-books-es.md)

The c++ contextual link did not work.
Merge pull request #528 from cmeraz/master

Added PHP section to spanish version (free-programming-books.md)
Update free-programming-books-de.md

Added missing Pro Git eBook with the german translation.
Fix two index links
Fix index link in ru file
Merge pull request #530 from Robalni/fix-ja-links

Fix two index links in japanese file
Merge pull request #529 from romankl/patch-1

Update free-programming-books-de.md
Web2Py thank to @mdipierro #526
Merge pull request #531 from Robalni/fix-ru-link

Fix index link in ru file
Update free-programming-books-zh.md

Codecademy is a very impressive online programming language learning system.
Merge pull request #533 from geekan/patch-1

Update free-programming-books-zh.md