Added support for :BYTE-COMPILE argument to compile-file. If T, we
byte-compile everything and create a machine-independent fasl file (dependent only on byte order.) If :MAYBE (the default, from ext:*byte-compile-default*), things are byte-compiled when speed = 0 and debug <= 1. Top-level forms are byte-compiled by default (controlled by ext:*byte-compile-top-level*.) Split IR2 trace-file dumping off from DESCRIBE-COMPONENT so that different back-ends can do different things.