format from the file contents ala emacs.

Check if "" (and "/") is in the list of directories and signal an
error so that we use the #P(...) syntax to print out the pathname
readably.

Update the pot and po files accordingly.

Catch the case of " " and signal an error so that we can print such
pathnames using the #P(...) syntax.  Also catch the case where the
directory includes an explicit directory separator, "/", which would
not be printed readably either.

Update the pot file too.

This change requires a cross-compile.  Use boot-2011-04-01-cross.lisp
as the cross-compile script.

bootfiles/20b/boot-2011-04-01-cross.lisp:
o New cross-compile bootstrap file

lisp/lisp.c:
o Recognize -unidata option and setup *UNIDATA-PATH* appropriately.

code/commandline.lisp:
o Add defswitch for unidata so we don't get complaints about unknown
  switch.

code/unidata.lisp:
o Rename +UNIDATA-PATH+ to *UNIDATA-PATH*, since it's not a constant
  anymore.
o Update code to use new name.

code/print.lisp:
o Update code to use *UNIDATA-PATH*

compiler/sparc/parms.lisp:
o Add *UNIDATA-PATH* to list of static symbols.
o Add back in spare-9 and spare-8 static symbols since we need to do a
  cross-compile for this change anyway.

compiler/x86/parms.lisp:
o Add *UNIDATA-PATH* to list of static symbols.
o Reorder the static symbols in a more logical arrangment so that the
  spare symbols are at the end.

i18n/local/cmucl.pot:
o Update

boot-2010-02-1 as the bootstrap file.  You should probably also use
the new -P option for build.sh to generate and update the po files
while building.