This resolves a PBD vs ARDOUR namespace error for some compilers:
```
error: reference to 'microseconds_t' is ambiguous
libs/pbd/pbd/microseconds.h:29:19: error: candidates are: typedef uint64_t PBD::microseconds_t
libs/ardour/ardour/types.h:81:29: error: typedef PBD::microseconds_t ARDOUR::microseconds_t
```
* Depending on individual strips to watch the selection property is prone to failure.
* Stripable_selection_changed() is called when a selection operation is completed.
Strips now maintain a pair of pending display strings (upper and lower).
A periodic timeout writes the pending value to the actual hardware if it
differs from the current string. This new design makes it easy to put a
message on the display and then after some period of time, revert to
whatever was there before.
* fixes Master Fader Touch button in the Mackie;
* implements a MasterFaderTouch global button;
* removes unused MackieControlProtocol::_transport_previously_rolling property;
* implements DeviceInfo::get_global_button() method;
* creates GlobalButtonsInfo and StripButtonsInfo types in DeviceInfo;
* implements Surface::_last_master_gain_written property to help master fader feedback;
* makes Surface respect _mcp.device_info().strip_cnt() to create master fader and when connecting signals for strips and master fader instead of using hardcoded 8;
* removed a few unnecessary updates in Surface::turn_it_on();
* included master_gain_changed() in Surface::periodic();
* implemented MackieControlProtocol::master_fader_touch_press and
* MackieControlProtocol::master_fader_touch_release;
git-svn-id: svn://localhost/ardour2/branches/3.0@12631 d708f5d6-7413-0410-9779-e7cbd77b26cf
* implements Metering on/off through Button::Read as per Seablade's suggestion. I choose this button as it's the "Show meters" button in Traktion;
* removes redundant code from Meter::update_transport_rolling();
* renames Meter::update_transport_rolling() to Meter::notify_metering_state_changed();
* renamed Surface::notify_transport_state_changed() to Surface::notify_metering_state_changed();
* renamed Strip::notify_transport_state_changed() to Strip::notify_metering_state_changed();
* created MackieControlProtocol::notify_metering_state_changed() and made MackieControlProtocol::notify_transport_state_changed() use it;
* implemented turning off of timecode display and two char display in Surface::zero_all ();
* implemented master fader zeroing in Surface::zero_all ();
* calling Surfaces->zero_all() at MackieControlProtocol destructor;
* implemented restore of 2nd LCD line content after metering being active.
git-svn-id: svn://localhost/ardour2/branches/3.0@12520 d708f5d6-7413-0410-9779-e7cbd77b26cf
