Check Description *after* %-expansion (want values not %exp token names)

For .info example:

  Description: PostgreSQL database adapter for Python %type_raw[python]
  Type: python (2.4 2.5)

Description is literally 57 chars in .info but only 42 chars for any
actual variant, and that latter is what matters

Closes https://github.com/fink/fink/issues/82
nee https://sourceforge.net/p/fink/bugs/1389/