Added symlink command to fix build error.

[chrislgarry]

Starting with FreeType 2.1.6, the old header file inclusion scheme is no longer supported. This will cause the build to fail if a symlink using the new scheme is not created before hand.

[chrislgarry]

NOTE: Starting with FreeType 2.1.6, the old header file inclusion scheme is no longer supported. This means that you now get an error if you do something like the following:

#include <freetype/freetype.h> #include <freetype/ftglyph.h>

This causes setup.py build to fail because some dependencies are using the old scheme above.

Details: http://freetype.sourceforge.net/freetype2/docs/tutorial/step1.html