1.10rc2: -D SYMBOL fails with default or negative value

[regregex]

1.10rc2 is not accepting a symbol definition from the command line without an explicit, non-negative value. 1.09 is known good. README.md defines the default value of symbol definitions to be -1, and both default and explicit definitions are rejected:

$ beebasm --help
beebasm 1.10rc2
...

$ beebasm -i edos.6502 -D _O2791S -D _SWRAM
Invalid -D expression: _O2791S

$ beebasm -i edos.6502 -D _O2791S=-1 -D _SWRAM
Invalid -D expression: _O2791S=-1

$ beebasm -i edos.6502 -D _O2791S=1 -D _SWRAM
Invalid -D expression: _SWRAM

$ beebasm -i edos.6502 -D _O2791S=1 -D _SWRAM=1
To coupon =&3746  Code size =&37FD

[mungre]

Oops! Thanks for the report. This is fixed by #84.

[regregex]

Woah, was about to submit a fix but you beat me to it! Great work, thanks.