Add make_all.sh script to build all configuration

This can be run to build all ports for all architecture
and C library combination.

I can also be used to build all combinations of just
one port.  e.g:

$ ./build_all.sh png

R=binji
BUG=None

Review URL: https://codereview.chromium.org/12041070

git-svn-id: http://naclports.googlecode.com/svn/trunk/src@683 7dad1e8b-422e-d2af-fbf5-8013b78bd812
Fix thttpd create_nmf code for multiple .nexe's

The library path was broken by recent changes.

BUG=None

Review URL: https://codereview.chromium.org/12036070

git-svn-id: http://naclports.googlecode.com/svn/trunk/src@684 7dad1e8b-422e-d2af-fbf5-8013b78bd812
Add libxml2 to naclports

R=binji
BUG=None

Review URL: https://codereview.chromium.org/12042076

git-svn-id: http://naclports.googlecode.com/svn/trunk/src@685 7dad1e8b-422e-d2af-fbf5-8013b78bd812