Additional BasicBlock reformatting
Replace macro BB_RESTART with private static method restart()
Drop macro BBB()
Replace macro BB_ADD with private static method append()
Replace macro BB_THREAD with private static method thread()
Cleanup
Merge pull request #906 from noakesmichael/bb-1

Continuing to prepare to extend BasicBlock to support marking essential expressions

Replace the BB macros with private static functions.
Other minor cleanup.

Compiled: STD clang/darwin, STD gcc/linux64, LLVM gcc/linux64
Tested: paratest
Review: None