variable parsing bug in 2.3.x

[Stefaan]

Well at least I think it is a bug:

Variable names apparently can no longer contain digits in 2.3.x
Convert-ly does not warn or change anything about offending definitions.

I have tried with the 2.3.6 package (i.e. the most recent one that is 
available in .deb format).

%% example: works in 2.2.3 but fails in 2.3.6 with "error: syntax
%% error, unexpected DIGIT, expecting '='"
%% on the line where v1 is defined.

v1 = \notes{a}
\score { \v1 }