update package x264
update package curl
update package libpng
package jpeg: fix missing stdio.h for FILE
update package libmng
package qtimageformats: libmng 2 compatibility
package qt: libmng 2 compatibility
package poppler: use lcms 2

Now that Qt uses libmng 2 which uses lcms 2, we should too.
package poppler: fix building poppler Qt 4 libraries

Poppler doesn't use qmake, so we resort to fixing the PATH so moc
can be found by the configure script.
package graphicsmagick: use lcms 2
package sfml: add *.pc file and use for test program
update package gnutls
new package libusb1

This is a package for the libusb-1.0 shared library (MXE package name
"libusb1") used by various projects. It is not to be confused with the
older libusb-0.1 library (MXE package name "libusb") which is a
completely different library with different API. Both libs are in
wide-spread use and can be installed in parallel.
mxe-activate: get targets from Makefile
mxe-activate: clear env vars on make invocation
mxe-activate: unset env vars for interactive use
mxe-activate: get targets from Makefile
Merge branch 'stable'
doc update: re-align requirements install commands
Merge pull request #227 from uwehermann/libusb1

new package libusb1