Remove custom Antlr dependency

[ahmetaa]

This issue is already solved but I created this issue for tracking purposes.

Custom Antlr dependency should be removed. We decided this because maintaining a patch of Antlr was time consuming. We use a patched Antlr version because original version was around 3 times slower. We may remove Antlr dependency alltogether in future releases because tokenization should be less strict and it should not do detailed classification.

[ahmetaa]

0a66952