(gdb-view-source, gdb-selected-view): New variables.

(gdb-view-source, gdb-selected-view): New variables.
(gdba): Inhibit DOS window in MS Windows.
(gdb-inferior-io-mode): Use hexl instead of cat.
(gdb-info-breakpoints-custom, gdb-assembler-custom, gdb-reset):
Use text in margin for MS Windows as there is no image support.
(gdb-restore-windows, gdb-setup-windows): Restore/start with
assembler view if appropriate.
(gdb-assembler-custom): Assembler code should display at point.
Parse address correctly.
(gdb-frame-handler): Accommodate selection of display of source
or assembler.
Add radio buttons to select display of source or assembler.