Makefile: add target loop, serialise targets, and update settings file
add mingw-w64 runtime and pthreads implementation, update related toolchain files
Makefile: not all packages have urls (i.e. pthreads) so remove check
various packages: enable/disable mingw-w64 builds
packages libgnurx lensfun: enable mingw-w64 build
various packages: enable/modify mingw-w64 build
Merge branch 'mingw-w64' into multi-rebase

Conflicts:
	Makefile
	src/plib.mk