add skip, anyCString, address prims

[raehik]

More binary primitives.

• skip :: Int -> Parser e () skip X bytes
• anyCString :: Parser e ByteString parse a null-terminated bytestring
• some parsers handling parser addresses directly (see below)

The Addr#-related primitives enable parsing structures like offset tables efficiently. We can "save" an Addr# via the withAddr# continuation, then use it in a lookahead together with an offset read from the input to jump around and parse arbitrary data elsewhere in the input. Some old code might explain better (function names are different): https://github.com/raehik/binrep/blob/180cd12c8fd773b0a99e5bb509432a2d0d11fae7/src/Binrep/Example/FileTable.hs#L81

TODO

• [x] perhaps rename the unsafe C-string parser. don't want to use # suffix for something that might not be useful anyway

[raehik]

snip, placed above

[raehik]

This will be a while while I fumble more primop compatibility helpers in.

[raehik]

This is ready - I'll write a few tests before merging, at least for C-strings and skips. The address stuff is harder to test and a lot less user-facing.

[raehik]

Fairly high confidence from the tests and these are very useful parsing primitives (I have been using them successfully via a fork). Merging!