check master sources when determining whether a region uses a source. should fix #5618
fix newly-appearing crash-at-close caused by muddled thinking in pbd/pthread_utils

threads created with this code can now just return a value as they normally would, and the
infrastructure will ensure cleanup. there is no longer any reason to call pthread_exit_pbd()
and so that has been removed.
update czech translations from pavel fric
update czech translations from pavel fric, part 2
undo the hiding of SR-dependent LV2 ports
don't run meter in import-dialog if the dialog is not visible
export: add support for CAF
fix confusion about whether flip_mode in the Mackie support code is a bool or an enum
pot/po file updates caused by waf i18n
free memory of external plugins on GUI close (major mem leak).

There is at least one known plugin that has a problem with this
(custom thread race condition) but it also crashes in other hosts:
http://www.drumgizmo.org/wiki/doku.php?id=bugs&do=showcaselink&showid=8&project=drumgizmo

tested to be working with various nedko, falktx and x42 plugins
add LV2 support for kx:external-ui#

the ABI of http://kxstudio.sf.net/ns/lv2ext/external-ui# is identical to
http://lv2plug.in/ns/extensions/ui#external
It just adds a distinction between #Host and #Widget for cosmetic reasons.
Sadly some newer plugins are released with only support for kxstudio URI :(
fix vari-speed phase (when used for calculation only)

and clarify an old comment.
update external plugin UI handling

amend to 4cdb018 and 1d972d0

override ui_closed() behavior for lv2ui:external
Keep UI around and do not re-instantiate, but simply show it again.
(this is against the original specs but was agreed upon by various
authors and the previous behavior or Ardour.)

kx:external-ui are cleaned up after ui_closed().
protect meters against weird float values
fix typo in IEC-meter 'weird-float' protection.
fix keyboard interaction with volume knobs (monitor section)
improve scroll and drag behaviour of volume-controller knob
LV2 external UI handling - revert to <= 3.3. behaviour

Don't ever clean up external UI plugins that use the LV2plug.in URI.
only free the memory of the last instance when the plugin is removed
or ardour closes.
LV2 extUI handling - amend to previous commit.
add std:: to clarify use of llabs on OS X