Include guilib/GraphicContext.h and don't assign NULL to int

Fixes: #14501
Merge pull request #2977 from smspillaz/fix-14501

Include guilib/GraphicContext.h and don't assign NULL to int
[configure] don't use relative include paths in addon headers
this breaks xbmc dev packages where all headers are installed in standard include paths
[configure] install missing addon bindings
Merge pull request #2964 from wsnipex/configure

[configure] don't use relative include paths in addon headers
fixed, signed/unsigned compiler warning
fixed, compiler warnings
[cddb] fix broken hello command should be as "cddb hello username hostname
clientname version"
[lang] update of internal addon language files
[lang] update of core language files
[lang] update of skin.confluence language files
[win32] fix library.xbmc.foo builds after cc988c14d2c13cee4633b316065e4cf335328e99
Fix for ignoring Protocol Options in CShoutcastFile::Open.
(something like UserAgent, Referer, etc.)
Merge pull request #2982 from SpiritOffice/ShoutcastFileOpenFix

Fix for ignoring Protocol Options in CShoutcastFile::Open.
add CONTRIBUTING.md with some basic information regarding pull requests
fix c/p screwup in CONTRIBUTING.md
[win32] add files created when running BuildSetup.bat to .gitignore
[lang] missing confluence home menu Dutch translations
Revert "[lang] missing confluence home menu Dutch translations"

This reverts commit ed2390f0823e6ec673884c72f0f93ff86adf285d.
[libdvdnav] re-enable reading DVD serial string