Bug 3098, Bug 3108, Bug 3545 -- Make MARC21 XSLT obey sysprefs in OPAC

Bug 3098, Bug 3108, Bug 3545 -- Make MARC21 XSLT obey sysprefs in OPAC

The MARC21slim2OPACDetail.xsl and MARC21slim2OPACResults.xsl XSLT
stylesheets do not obey any of the OPAC sysprefs, OPACURLOpenInNewWindow,
URLLinkText, or a new one added for Bug 3545, DisplayOPACiconsXSLT.
Modified C4/XSLT.pm based on code written by Fréric Demians (thanks!) to
pass the values of the sysprefs to the .xsl files.  Modified the .xsl
files to implement them.  If the respective sysprefs are set, the OPAC
results and display pages will/will not display the format/material
type/audience icons, will/will not open URLs in new browser windows,
and will/will not use the text entered in URLLinkText as generic link
text when there is no value in the 856 subfield y, 3, or z.  (Note that
if subfields y, 3, or z do contain text, the first match is what will be displayed.)

Signed-off-by: Galen Charlton <gmcharlt@gmail.com>