* Finish the man pages.

* Create a user's guide or tutorial.

* Create a generic "get preferred" function that accepts a type a
parameter.  This function can then be used to retrieve the preferred
EMAIL, TEL, ADR, LABEL, and possibly URL.

* Have the type name, param name, and param values all stuffed into
the vc_component as lowercase-only values.  This will simplify the
searching and comparison of these values and eliminate the need for
strcasecmp in a lot of places.

* Consider applying the patches in the patches/ directory, which were
taken from from https://github.com/yourealwaysbe/libvc:

- https://github.com/yourealwaysbe/libvc/commit/5942b62db420781f3598ccc35b560bf66dc39965

This one improves the parsing times of large vcards and has a
significant impact.

- https://github.com/yourealwaysbe/libvc/commit/d72dfdcf5722884a1fe79ea41343baa3673786a1

This one is necessary for fixing segfault caused by the previous patch.

The problem with this patches is that the ABI is changed in (probably)
and non-backward compatible way.

* When doing "make clean", remove the automatically generated files
  src/vc_parse.c, src/vc_parse.h, and src/vc_scan.c.

* Consider removing the calls to exit() in function vc_new().
