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/inline-4.out

@@ -22,7 +22,7 @@ default
                     }
                 }
                 {
-                    jump ___lbl__00001;
+                    ;
                 }
                 @___lbl__00001;
                 {
@@ -35,7 +35,7 @@ default
                     {
                         {
                             ___ret__00002 = llGetLinkNumber();
-                            jump ___rtl__00006;
+                            ;
                         }
                     }
                     @___rtl__00006;
@@ -43,7 +43,7 @@ default
                 while (___ret__00002);
                 {
                     ___ret__00001 = <((float)0), ((float)0), ((float)0)>;
-                    jump ___rtl__00004;
+                    ;
                 }
             }
         }

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;
+
+}}

unit_tests/coverage.suite/jump-opt.skp

@@ -0,0 +1 @@
+This optimization is not implemented.