(mh-tool-bar-define): Fix XEmacs' vector-list so it refers to the

(mh-tool-bar-define): Fix XEmacs' vector-list so it refers to the
icons in mh-xemacs-icon-map instead of trying to declare the icons in
situ. This allows mh-tool-bar.el to be compiled under XEmacs. Remove
initial value for mh-tool-bar-folder-buttons,
mh-tool-bar-show-buttons, mh-tool-bar-letter-buttons. The MH-E icons
now appear in XEmacs. In mh-tool-bar-init, check for
mh-xemacs-use-tool-bar-flag sooner. This allows MH-E to be used in
XEmacs in a tty (closes SF #1506846).