(gdba, gdb-assembler-mode): Call the mode "Machine" as

(gdba, gdb-assembler-mode): Call the mode "Machine" as
a mode called "Assembler" already exists.
(gdb-use-colon-colon-notation, gdb-show-changed-values): New
options.
(gud-watch): Use format option. Remove font properties from
string.
(gdb-var-create-handler, gdb-var-list-children-handler): Don't
bother about properties as there are none.
(gdb-var-create-handler, gdb-var-list-children-handler)
(gdb-var-update-handler): Call gdb-var-evaluate-expression-handler
with two arguments.
(gdb-var-evaluate-expression-handler, gdb-post-prompt): Let
speedbar show value changes with a different font.
(gdb-edit-value): New defun.
(gdb-clear-partial-output, gdb-clear-inferior-io)
(def-gdb-auto-update-handler): Use erase-buffer.
(gdb-frame-handler): Display watch expressions in
FUNCTION::VARIABLE format if required.