This reverts commit 0b1f4248, which appears to
be a bogus fix (for a bogus warning?).  Also needs adaption a la
3c598c40 "sal: work around spurious signed
overflow warnings."

Conflicts:

	sal/inc/rtl/ustring.hxx

Change-Id: I7e9d94fd93a37bb10604c1895ab619a8ac2c3f43