Use updated Glyphicons to workaround old Android WebKit bug

Fixes #10106.
There is a backwards-compatibility concern here, in that the codepoint changes will break stuff that uses the codepoints directly (e.g. entering one directly into HTML, using an `&`-escape to represent one in HTML, writing a custom `.glyphicon-*` equivalent, etc.), as opposed to our `.glyphicon-*` classes.
On the other hand, we didn't document the codepoint numbers or recommend usage of them, so they are arguably not part of our public "API".

(Note: I don't have an Android device of appropriate vintage, so I can't fully test this myself. But the changes make sense theoretically, and I have tested that the icons still display fine on unaffected browsers.)