osx: add OSX integration with native GTK library

Add integration with native OS X menu and native
fullscreen mode for main window.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
osx: make sure that dialog windows are menu-less

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
osx: make inputdialog menu-less

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
osx: disable menu when quicksearch input field is in focus

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
osx: set address book specific menubar as application menu

makes AddressBook menubar appear as application menu when
AdressBook window is open.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
osx: add 'make bundle' target to build OS X application bundle

creates application bundle claws-mail.app at $HOME/Desktop/

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
osx: make sure that enchant modules are in bundle and could be found

patch relies on libenchant recognizing ENCHANT_MODULE_PATH env variable,
which is provided by off-tree patch to libenchant which comes together
with jhbuild moduleset build file for clawsmail.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
osx: add jhbuild moduleset file with dependencies to simplify claws-mail build

with this claws-mail could be build within preinstalled
gtk-osx env using following command:

  jhbuild build claws-mail_jhbuild.modules

Signed-off-by: Igor Mammedov <imammedo@redhat.com>