add release-build logging capabilities

Some bugs only reproduce in release build, and in other scenarios some basic statistics beyond the "rstats" are desired for release build. This is a feature request for some kind of logging support in release build. Of course if such support goes too far it might trigger whatever overhead and timing changes make a bug not reproduce in debug build.

We might want to disable per-thread files for release-build logging if we can't hide the evaluation of the dcontext lookup behind the log-enabled check, or even if we can to reduce some overhead (though once enabled i/o will likely shadow it).

We may want to measure the cost of a global log-enabled check in every LOG location on a worst-case benchmark like continued process spawning.

We will have to figure out how to deal with debug-build-only data structure fields. One way is to go the RSTATS route and have RLOG which works in both release and debug.