[TASK] Split t3lib/config_default.php code into functions

Step to a cleaner bootstrap in config_default.php: Split the
code segments into functions and call them. Do not worry about lots
of global functions, they will be moved to the bootstrap classes
with the next patches.

Change-Id: I0e00ad575d081688e0dcee58a7293d523a5d999a
Resolves: #38106
Releases: 6.0
Reviewed-on: http://review.typo3.org/12118
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Tested-by: Susanne Moog
Reviewed-by: Susanne Moog
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn