Fix merge of sgml-syntax-propertize-rules

During the merge of emacs-26, the sgml-syntax-propertize-rules part of
2019-01-17 "* lisp/textmodes/sgml-mode.el: Try and fix bug#33887." got
lost in the conflict against 2019-05-09 "Recognize single quote
attribute values in nxml and sgml (Bug#35381)".
* lisp/textmodes/sgml-mode.el (sgml-syntax-propertize-rules): Reapply
the 2019-01-17 change to speed up sgml-syntax-propertize-rules, taking
into account the 2019-05-09 which means we have to handle single
quotes as well.
1 job for master in 50 minutes and 3 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #1772
test-all

00:50:03

 
Name Stage Failure
failed
test-all Test
make[2]: *** [check-doit] Error 1
Makefile:318: recipe for target 'check-doit' failed
make[2]: Leaving directory '/builds/emacs/emacs/test'
Makefile:293: recipe for target 'check-expensive' failed
make[1]: *** [check-expensive] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/test'
Makefile:957: recipe for target 'check-expensive' failed
make: *** [check-expensive] Error 2
ERROR: Job failed: exit code 1