Fix memory issue in AntlrInput::parseError (#4873)

Fix memory issue in AntlrInput::parseError (#4873)

The `parseErrorHelper` message can run into memory errors when the it prints the last line and this last line is not terminated by a newline. I suspect other conditions may trigger it as well (like only using `\r` as line terminator).
This comit computes the size of the buffer from the start of the current line to the end of the buffer and makes sure that we never go beyond this buffer. The calculation looks a bit awkward, I've not been able to obtain this information from the ANTLR input stream in a nicer way...
(I found this issue when looking at #4866).
Fixes #4069 .