Code Cleanup

- Renamed files task.h -> main.h, task.cpp -> main.cpp.  This is to
  prepare for the next rename, which addresses the OpenBSD bug.
- Removed utf8.h, utf8.cpp from Makefile.am, which were inadvertantly
  added.

src/Makefile.am

@@ -4,9 +4,9 @@ task_SOURCES = Att.cpp Cmd.cpp Config.cpp Context.cpp Date.cpp Duration.cpp   \
                Record.cpp Sequence.cpp StringTable.cpp Subst.cpp T2.cpp       \
                TDB2.cpp Table.cpp Timer.cpp color.cpp command.cpp edit.cpp    \
                import.cpp interactive.cpp parse.cpp recur.cpp report.cpp      \
-               rules.cpp task.cpp text.cpp utf8.cpp util.cpp                  \
+               rules.cpp main.cpp text.cpp util.cpp                           \
                Att.h Cmd.h Config.h Context.h Date.h Duration.h Filter.h      \
                Grid.h Keymap.h Location.h Nibbler.h Record.h Sequence.h       \
                StringTable.h Subst.h T2.h TDB2.h Table.h Timer.h color.h      \
-               i18n.h task.h text.h utf8.h util.h                             \
+               i18n.h main.h text.h util.h                                    \
                T.cpp T.h TDB.cpp TDB.h