Also, use '^' to escape newlines in appveyor-install.bat to avoid an
absurdly long line, remove some unnecessary quotation, and alphabetically
sort packages
Also, define the _XOPEN_SOURCE feature test macro in the boost test to avoid
'not declared in this scope' warnings for pthread_rwlock_init(), etc.
This reverts commit 92c2bb7519.
This is no longer needed, as a patched ninja is now available from the
standard Cygwin package repository, and prevents me from accidentally
breaking CI when changing things in my personal package repository.
* Install pip on msys (which doesn't have it)
* Install codecov/coverage everywhere.
* Generate coverage XML file manually because codecov tries to call the
coverage script itself and it's in a weird place on the path.
GoaLitiuM