When finding matching icon sources or cached icons, any scale greater than
1.0 should be treated as 2.0. This is imporant for Windows where scales can
be things like 1.25 or 1.5.

This doesn't do anything for us on Mac. I'm putting this into bockbuild
basically to have one less patch that diverges for us between Mac and Win32.
Set PREFIX in make as well as makeinstall
Include PCL assemblies in md-dev-env
Restore generation of Xamarin PCL SupportedFrameworks files
Merge branch 'master' into alexischr-mono-mac-64-package