Added/updated libraries: zlib, freetype, libpng, libiconv, gd

Bumped zlib version from 1.2.3 to 1.2.7
Bumped freetype version from 2.1.4 to 2.4.9
Added libpng 1.5.10
Added libiconv 1.14
Added gd 2.0.35

Only build static versions of these libraries
  (why would nestedvm ever need shared libs?)

Updated sourceforge download URL prefix

Commented out old freetype patches that I don't understand
and don't apply cleanly.  Tests seems to work OK.

Patched freetype test program to use newer (mandatory) include syntax