Add LITERALPLUS support.
Add LITERALPLUS support.

In imapx_command_start(), just keep calling imapx_continuation() to send
the continuations immediately.

For this, we have to pass the CamelIMAPXServer pointer in to
camel_imapx_command_new() so that it can see the server's capabilities.

gcampax/evolution-data-server,gcampax/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server,gcampax/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,gcampax/evolution-data-server