Fix: mb_strtolower function does not exists on all PHP versions.

Conflicts:
	htdocs/core/lib/pdf.lib.php
Fix: Log of leaves was broken on some mysql versions.
Merge remote-tracking branch 'origin/3.5' into 3.6
Merge remote-tracking branch 'origin/3.6' into develop

Conflicts:
	htdocs/holiday/class/holiday.class.php
Fix: Table holiday_user was not initialized anymore.
Add table llx_holiday_types to store type of leave.