speed up front end by manually simplifying the pattern replacement pass

this cuts about 20% off code loading time and sysimg build time
speed up front end by manually simplifying the pattern replacement pass

this cuts about 20% off code loading time and sysimg build time
Merge branch 'jb/frontendopt' of github.com:JuliaLang/julia into jb/frontendopt
fix some error checking in optimizations to front end