[TYPO3-core] hardcoded typo3 directory

[Tomasz Krawczyk]

Hello

There is a lot of places where string 'typo3/' is hardcoded in the core.

First I thought that applying Christian patch by changing 'typo3/' with 
constant TYPO3_mainDir will simply resolves the problem.  Yesterday 
Markus in the bug http://forge.typo3.org/issues/20031 noticed that there 
may be more problems with this. The problem may also happen with 
extensions and their BE modules.

There is the chapter "Changing the default “typo3/” directory" in 
doc_core_inside. Coexisting hardcoded 'typo3/' in the core and this 
chapter is misleading.

I think one of two things should be done chapter removed or global 
constants should be used. I don't know maybe information in the Coding 
Guidelines.

What do you think guys?