Remove IRScope::end

Specifying the basic block before which to insert the new one
is not mandatory when calling llvm::BasicBlock::Create. This
was the only use of the tracked "end" block. The concept was
phony anyway because there is no single "end" to a scope with
unwinding and so on.

For prettying up the IR, it is possible to change the order
of basic blocks using move{Before, After}().

ir/irfunction.cpp

@@ -119,7 +119,7 @@ void FuncGen::prepareToDestructAllTemporariesOnThrow(IRState* irState)
 
     // create landing pad
     llvm::BasicBlock* landingpadbb = llvm::BasicBlock::Create(irState->context(),
-        "temporariesLandingPad", irState->topfunc(), irState->scopeend());
+        "temporariesLandingPad", irState->topfunc());
 
     // set up the landing pad
     landingPadInfo.addFinally(callDestructors, /* deleteOnPop = */ true);