make source map incremental compilation support even more
robust. previously source map support would not work for incremental
compilation across JVM runs. Now compiler tracks which files it has
seen, if a file has never been encountered and source maps are enabled,
then it will trigger a recompile, under :optimizations :none just checks
for existence of the corresponding .map file for each compiled .cljs
source file.

java.io.File -> File in compiler.clj

now that incremental compilation is more robust, remove reset hacks for
:optimize-constants and :advanced.