Changes needed to accommodate building libevoral with MSVC

Note that class 'MusicalTime' needn't be exportable (with a little work, this could be reverted if it affects the other builds)
Remove a commented out line in 'pbd/stacktrace.h'

(was probably just needed for testing at some stage)
Simulate 'trunc()' which isn't available in MSVC

(needed by 'gtk2_ardour/editor.cc')
Now that we're building pango's language modules statically (i.e. no longer as DLLs) it's not necessary to edit the user's 'pango.modules' file
Add a newly introduced header file to our MSVC project (gtk2_ardour)
fix OSX open URL in browser
when dragging on the canvas, use x,y pointer coordinates to decide if motion has occured.

Using _last_pointer_frame breaks when dragging to the left of the canvas, because we clamp
the value of the frame to >= 0. Motion would step once the pointer crossed the left edge
of the canvas because the frame value would always be zero.

This is not a problem when using the pointer x,y values which end up appropriately negative
under all conditions.
Fix clang check for versioned clang executables.
Don't add non-clang flag regardless of platform.
Shup up clang about gtkmm/papertraits.h.
Remove dead code.
Check for clang with an actual code check.

Turns out Apple in its infinite wisdom installs clang as /usr/bin/g++, so
guessing based on executable name doesn't work.
NOOP, fix some “missing sentinel” -Wformat
quick sanity check
[Summary] Fixing behavior of the FloatingTextEntry
fix case of included header file
fix indentation nightmare from 9559cf3947
Revert "Don't add non-clang flag regardless of platform."

Apple's g++ on 10.6. does not understand -Wno-unused-local-typedefs
either

This reverts commit 9dd8024e41f35e581b3db5f4a873126398db9d45.
Fix order of parameters to stop_touch() in Mackie::Control

Reverse the parameters of Mackie::Control::stop_touch() to make them
consistent with AutomationControl::stop_touch(), and fix up the call to
AutomationControl::stop_touch() to have the parameters in the correct
order.

Unfortunately, I don't possess any devices that speak the Mackie protocol, so
though the patch seems logical and correct to me, I have no way of testing it.
If anyone has a device with touch faders that speaks Mackie, I'd be glad of any
confirmation that it at least doesn't break anything.
Fix build of evoral tests

Fix compile errors in libs/evoral/test/, by explicitly calling
Evoral::MusicalTime::to_double() wherever a double value is required of a
MusicalTime.

Some of the double variables should probably really be made into MusicalTime
ones instead, but I don't want to mess with this too much.

takeFiveTest still fails for me after this, but a failing test is probably
more informative in the long run than a test that won't even compile.