dyndbg: refine export, rename to dynamic_debug_exec_queries()

commit 4c0d7782 ("dyndbg: export ddebug_exec_queries") had a few
problems:
 - broken non DYNAMIC_DEBUG_CORE configs, sparse warning
 - the exported function modifies query string, breaks on RO strings.
 - func name follows internal convention, shouldn't be exposed as is.

1st is fixed in header with ifdefd function prototype or stub defn.
Also remove an obsolete HAVE-symbol ifdef-comment, and add others.

Fix others by wrapping existing internal function with a new one,
named in accordance with module-prefix naming convention, before
export hits v5.9.0.  In new function, copy query string to a local
buffer, so users can pass hard-coded/RO queries, and internal function
can be used unchanged.

Fixes: 4c0d7782

 ("dyndbg: export ddebug_exec_queries")
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20200831182210.850852-3-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>