Incorrect parsing of overlay char '0' to '9' in compressed positions

[F4FXL]

Hi,

When parsing a compressed frame using overlay chars in range '0' to '9' est wrong overlay char is returned.

In compressed format overlay char '0' to '9' are sent as 'a' to 'j' e.g. a station using '1' as an overlay will send an actual 'b', this has to be converted back into '1' when parsing.

I think the issue is occurring here

aprs-python/aprslib/parsing/position.py

Line 100 in c2a0f18

symbol_table = compressed[0]

where first char is just copied into symbol table.
A test shall be added to see if compressed[0] is in range 'a' to 'j' and change it to '0' to '9'.

[F4FXL]

Maybe something like this:

symbol_table = compressed[0]

if 'a' <= symbol_table <= 'j':
    symbol_table = chr(ord('0') + (ord(symbol_table) - ord('a')))