commit: UT_String class

[Mike Nordell]

In src/af/util/xp we now have four new files
ut_string_class.cpp
ut_string_class.h
ut_stringbuf.cpp
ut_stringbuf.h

I also updated Makefile and Makefile.mpw (I _think_ I got the Mac. EOLs
right).
/MSVC6/AbiUtil.dsp is also updated.

/Mike