Add record_start and record_stop functions.

Signed-off-by: Tim Wiederhake <tim.wiederhake@intel.com>

gdb/ChangeLog

	* record.h (record_start, record_stop): New export.
	* record.c (record_start, record_stop): New function.

Change-Id: If235d4bde8ec61dab6dbd23e087430e66d2e91a7