show benchmark subtotal (#2960)...At the end of the benchmark, sums of the input, output and
gzip values are shown, such as:
Subtotal
Original: 7785102 bytes
Uglified: 2283862 bytes
GZipped: 662354 bytes
relax `collapse_vars` on `AST_Exit` (#2855)...First introduced in #1862 to stop assignments to migrate beyond `return` or `throw`. Since then `collapse_vars` has been improved to handle various side-effect-related corner cases.