basic block must end with a terminator instruciton (such as a branch) ->
when emitting a label, check whether the previous instruction is a
terminator instruction and if not, add an unconditional branch to the
label we are adding.
o Implemented at the tcg instead of at the thlcgobj level because
a) these methods don't need any high level type information
b) implementing them in thlcgobj would require making thlcg.a_label()
virtual and ensuring that no-one ever calls cg.a_label() in any
generic code
git-svn-id: branches/hlcgllvm@26038 -