Created by: cvrebert
Fixes #10106 (closed).
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.)