"interesting_blocks" is only used inside tree-into-ssa.c, so it can be
made static.

Successfully bootstrapped on x86_64-unknown-linux-gnu (using
gcc-4.7.2-2.fc17.x86_64).

OK for trunk?

2013-06-07  David Malcolm  <dmalcolm@redhat.com>

	* tree-into-ssa.c (interesting_blocks): Make static.