Support `xstring` and `string_table` as input for parser

[mbtools]

Allows several types of input instead of just string.

Closes #189

PS: Cosmetic change for type constants

[sbcgua]

:+1: will have a look during the weekend.

"PS: Cosmetic change for type constants" - oops :)

[sbcgua]

Hi Marc, sorry for the long delay. Just lack of time and energy ... :/

Good PR, merging ...

Perf test just for info (minor perf impact - insignificant for the test cases, hopefully they are relevant enough)

Before

After

[sbcgua]

hopefully will count to hacktober?