Build libedbus-private.la as a shared library

This fixes an issue under Win32, where symbols from library are
linked multiple times into the final executable (like into
evolution-source-registry), which causes a runtime error about
registering EDBusObject type multiple times on start.
Bug 733733 - Crash due to write out of buffer in CamelMimeFilterToHTML
Do not add GTasks source when the GTasks backend is not built

It was causing an error "Unable to connect to 'Tasks': No backend
factory for hash key 'gtasks:VTODO'" when this source was selected
in UI, because the source was added unconditionally, while
the backend itself is built with libgdata 0.15.1+ only.
Bug 735523 - test-book-client-custom-summary: Add 'exists' tests

... for email and X509 certificates.
Bug 735523 - EBookSqlite: Support 'exists' queries from summary
Bug 735523 - EBookSqlite: Support boolean summary field for EContactCert

We don't actually care about summarising the *data*; merely indicating
the *presence* of the field is sufficient. With the new evolution-pkcs11
module, the 'exists(x509Cert)' query is going to get very hot...

This halves the time it takes to query the Intel global addressbook,
with almost quarter of a million entries of whom about 5% have
certificates listed.
Bug 735523 - EBookSqlite: Enable x509Cert summary field by default

Again, evolution-pkcs11 is going to make 'exists(x509Cert)' a *hot* query...
Bug 735200 - [IMAPx] Fails to handle QUOTA response with no quotas

The untagged QUOTA response includes a list containing quota usage and
limits for each quota resource for which a limit applies. Per RFC 2087
section 5.1, "The list contains zero or more triplets.".

Fix the parser to handle an empty list. Additionally, when the IMAP
server supports the quota extension but reports no quotas for a folder,
return G_IO_ERROR_NOT_SUPPORTED rather than G_IO_ERROR_NOT_FOUND, since
Evolution (and maybe other callers) special-cases the former error code.