parse: Replace 'Begin' with 'Start' in keywords ...

Okay, it's to the point I'm writing bugs in tests due to this.
Just change it already.

tests: Add regression test for trailing whitespace in text

parse: Fix text literals being cut off when placed at end of file

parse: Account for EOF when checking for whitespace ...

When parsing a file that doesn't end with whitespace (like a new line),
the parser would choke on having no symbols left. Fix that.

Fixes: 1519cef