Add missing include path to naclports that need pepper headers.

The latest SDK includes the pepper headers just once in
${NACL_SDK_ROOT}/include and this is not on the include
path by default.

Also, fix issues resulting from the new headers including
all interface versions simultaniously.

TEST=make all

Review URL: https://codereview.chromium.org/11827054

git-svn-id: http://naclports.googlecode.com/svn/trunk/src@653 7dad1e8b-422e-d2af-fbf5-8013b78bd812