* "push<anything>;pop" can be removed (if there's no jumppoint)
* "push<anything>;coerce;pop" can be removed (if there's no jumppoint)
* "getlocal_i;pop" can be removed
* "goto next;next:" can be removed (if there's no jumppoint)
* "setlocal_i;getlocal_i" can be changed to "dup;setlocal_i"
* for a variable without any getlocal_i, all dup;setlocal_i can be removed
* getlocal <i> can be changed to getlocal_i for i<4, same for setlocal
* greater followed by iftrue can be reduced to ifgt
* equals followed by iffalse can be reduced to ifne (etc.)
* callproperty;(coerce);pop can changed to callpropvoid
* label can be removed
* "getlocal_i;setlocal_i" can be removed
* "dup;xxx;pop" can be reduced to xxx (xxx=setlocal_i, setglobalslot, pushscope)
* "getlocal_i;increment;setlocal_i" can be replaced by inclocal_i
* [iffalse xx;jump yy;xx: -> iftrue yy]
* a jump to a jump can be redirected
* sort variable indices by usage
* coerce*;returnvalue can be reduced to returnvalue
* a kill before a return can be eliminated
* setlocal_i;getlocal_j;getlocal_i can be changed to dup;setlocal_i;getlocal_j,swap (makes it possible to remove i if not otherwise used)