(gdbmi-send): Improve regexp to repeat commands.

(gdbmi-send): Improve regexp to repeat commands.
Try to deal with continuation line.
(gdbmi, gdbmi-prompt1, gud-gdbmi-marker-filter): Update to new
variable names.
(gdb-break-list-regexp, gdb-stack-list-frames-regexp):
Future proof against new fields being added to MI output.
(gdbmi-prompt2, gdb-break-list-handler,gdb-get-source-file)
(gdbmi-frame-handler): Update to new variable name
gdb-get-buffer-create.
(gdbmi-frame-handler): Use hollow-right-triangle for all selected
frames which except the innermost (where execution has stopped).