copy v1 to create v2
Apply Bard's changes from
git@github.com:10gen/mms-automation.git/go_planner/src/com.tengen/cm/util/slogger.go
commit 14f4b118b15616d2594d8497655cc22eb4a11229 to v2

This adds the ability to ignore certain filenames when logging the
caller (works well when building a logging system on top of slogger)

Also adds ROUTINE and DOOM log levels.