Updated MARC21slim2MODS3-4.xsl to version 1.93

From the MODS list:

MARCXML to MODS 3.4 -- XSLT 1.0 (Revision 1.93) Announcement

The Library of Congress' MARCXML to MODS 3.4 (XSLT 1.0 Revision 1.93) is now available via the Library of Congress' MODS Web site and at http://www.loc.gov/standards/mods/v3/MARC21slim2MODS3-4.xsl --it incorporates edits made in response to comments received since the release of Revision 1.86. Thank you for all your comments over the last few months.

The MODS 3.4 XSLT is based on the MARC to MODS 3.4 mapping made available by the Library of Congress and last updated in July of 2013 <http://www.loc.gov/standards/mods/mods-mapping.html>.