HTML 4.01 don't seem to require the http-equiv value to be quoted, so
make the quotes optional.
Also allow more than one space between the meta tag and its http-equiv
attribute.

Closes #3300703.

git-svn-id: https://geany.svn.sourceforge.net/svnroot/geany/trunk@5796 ea778897-0a13-0410-b9d1-a72fbfd435f5