Perform redundant jump elimination in lastpass

This is a first try at redundant jump removal (jumps that target the very next instruction). It's too basic in several ways.

- The statement is replaced by a ';' instead of removed.
- If the jump was the only statement in an if, when the if becomes empty, it's not folded.
- Jumps that are last in the 'then' branch of if+else are not visible. This would need either to track multiple last statements, or to have some means to anticipate what the next statement is at every statement. A Control Flow Graph would help a lot.
- When a label is immediately followed by a jump, all jumps to that label should target the destination of that jump if it's in scope. Added to TODO.
- It misses some optimizations when not expanding WHILE and FOR into IF/JUMP.

Moving everything to an earlier stage would help with some of these, especially with ';' and 'if' folding. Unconditionally expanding WHILE and FOR would also help.

unit_tests/coverage.suite/jump-opt.lsl

@@ -0,0 +1,13 @@
+default{state_entry(){
+
+    if (llGetLinkNumber()) jump x1;
+    if (llGetLinkNumber()) jump x1; else jump x3;
+
+    llOwnerSay("ok");
+    @x1;
+    jump x2;
+    @x3;
+    llOwnerSay("blergh");
+    @x2;
+
+}}