Update SPL to use new debug infrastructure. This means:

• Replacing all BUG_ON()'s with proper ASSERT()'s
• Using ENTRY,EXIT,GOTO, and RETURN macro to instument call paths

git-svn-id: https://outreach.scidac.gov/svn/spl/trunk@78 7e1ea52c-4ff2-0310-8f11-9dd32ca42a1c