Added a function profile_with_exn_name that keeps track of exception names in
the profiling results. In contrast, profile_with_exn combines all exceptions
raised by foo in one entry, foo_exn.

added real-time to profiling information

added functions to profile with respect whether a function failed (threw an exception) or terminated normally

Column width in profiling output is now computed dynamically. Leads to much nicer output when there are big numbers (i.e., long strings) which wouldn't fit before.

Move Profile.sig and Profile.sml to portableML, as this code has
nothing in it that is HOL specific. (Indeed, it's not used much in
the code base at all as it's a pretty poor man's substitute for real
profiling.)