Implement PrintableASTNode and PrintableStmt.
I miss these whenever I'm doing printf debugging, so I thought
I'd implement them once and for all. No functional change.

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@540 812d1f90-f944-d88a-411a-122bdc93e1ea
Sort using declarations. No functional change.

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@541 812d1f90-f944-d88a-411a-122bdc93e1ea