libffi: Fix 32-bit builds
libffi: Fix 32-bit builds

We need to use the same workaround for Visual Studio 2015 for 32-bit MASM
source files, and the property sheets missed that portion.  D'OH!

fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects,fanc999/gtk-msvc-projects