Add discid_get_toc_string() to get 'toc=...' string alone.

Use it in create_submission_url() and create_webservice_url(), reducing
code redundancy.
Calculations of buffers length was slightly modified to be safe.
Adjust buffer sizes
Allocate memory in create_toc_string() and allow to pass a string separator.
create_toc_string(): do not allocate more than needed.

Size calculation is commented.
Add discid_get_toc_string()
Fix comments
include libmusicbrainz usage example (web_query)
don't fail if libmusicbrainz isn't found

We only need the library for an example
and don't actually require it.
So be quiet about searching it.
build disc_metadata also with autotools

The key is that libmusicbrainz5 should *not* be added to LIBS,
because that would link libdiscid to it!
Merge pull request #1 from JonnyJD/libmusicbrainz

LIB-54: Add libmusicbriainz / query metadata example
Merge branch 'tocstring'

see pull-request #34 and LIB-41

Conflicts:
	src/disc.c
add tests for TOC string API
update ChangeLog with changes in master