Fix runtime libraries find and installation
* m4/gpg4win.m4(GPG4WIN_RUNTIME_LIBRARY): New. Helper for runtime libraries. Searches more locations. * configure.ac: Use above and add libwinpthread-1.dll dependency * src/inst-gpg4win.nsi: Install libwinpthread-1.dll. Move runtime libs from pub to top level install dir. * src/uninst-gpg4win.nsi: Uninstall runtime libs from their new location.
This also fixes the problem that libraries were not reported as
missing when no other missing tools were found missing.