Fix compilation on linux now that libardour no longer links to libjack

Similar change has already been made in master branch
Revert unfinished export visibility commits by John Emmas

These break the mingw build and the visibility work will make this
code redundant
Remove duplicate ALSA pkgconfig
Use PBD::pthread_name in MTC_Slave for portability
Include pbd/localtime_r.h in session_jack.cc for MinGW
Use PBD::canonical_path instead of ::realpath

This is a previous change that seems to have been lost in master -> windows merge
Waf options are not valid during build stage so use environment variable
Fix pattern used to search for audio backends on windows

The audio backend dlls have a number postfix after the library/module name
Remove command line string quoting when forming jack command line on windows

This used to be necessary when we started the JACK server but now that we
write a .jackdrc it only causes problems.

I have fixed this before in some branch, must have been lost in a merge.
Replace non-portable printf format specifier

This caused Diskstream state to be restored incorrectly
Use Sleep instead of usleep on windows in JACK backend
Reinstate call to package config for JACK backend

Not sure how this got lost, merge perhaps.
Merge branch 'windowspush' of https://github.com/mojofunk/ardour into windows
switch from using Sleep/usleep to Glib::usleep()
switch from using Sleep/usleep to Glib::usleep() (and remember that we need to make Glib::usleep() actually work on windows one day)