(GDB/MI): Remove duplicate acknowledgements.

(GDB/MI): Remove duplicate acknowledgements.
(GDB/MI Simple Examples): Move node up one level.  Use real examples.
(GDB/MI Compatibility with CLI): Update.
(GDB/MI Result Records): Add "connected" and "exit" result classes.
(GDB/MI Stream Records): Clarify target output.
(GDB/MI Command Description Format): Modify example description.
(GDB/MI Breakpoint Table Commands): Rename to...
(GDB/MI Breakpoint Commands): ...this
(GDB/MI Breakpoint Commands): Add optional thread field.
(GDB/MI Program Control): Add an introduction.  Move "Program
termination" examples into exec-run description.
(GDB/MI File Commands): Mention similar CLI commands.
(GDB/MI Miscellaneous Commands): Move to end.  Mention "show version"
is similar to "-gdb-version".