XWIKI-11300: Glyphicons are not loaded on a subwiki using a custom skin based on Flamingo and stored in the main wiki.

(cherry picked from commit c829ca2b3f3ae671d0198e2969c9fe1ec42a05f8)

Conflicts:
	xwiki-platform-core/xwiki-platform-containers/xwiki-platform-container-servlet/src/main/java/org/xwiki/container/servlet/filters/internal/SetHTTPHeaderFilter.java
	xwiki-platform-core/xwiki-platform-web/src/main/webapp/WEB-INF/web.xml