[Distutils] Version numbers with a letter at the end

[Ben Bangert]

Does setuptools distinguish and recognize letters in a version?

For example, the latest Myghty is:
   version='0.99a'

When I up it to '0.99a.1', and setuptools does a pre-requisite check,  
it doesn't seem to recognize that 0.99a.1 is more recent than 0.99a.  
Also, this seems like it would cause problems with requirements that  
look for a dev version, as it'd be:
"Myghty >= 0.99.adev-r1980"

Is a numerical-only version number a requirement for version info  
under setuptools?

- Ben