Implement the "&&" and "||" operators

Implement the "&&" and "||" operators

This implements the "&&" and "||" operators.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* expop.h (class logical_and_operation)
	(class logical_or_operation): New.
	* eval.c (logical_and_operation::evaluate)
	(logical_or_operation::evaluate): New methods.
	* ax-gdb.c (logical_and_operation::do_generate_ax)
	(logical_or_operation::do_generate_ax): New methods.