The hardcoded 'memcpy' name turns up in other derived tests like
mempcpy.
* benchtests/bench-memcpy.c (test_main): Use TEST_NAME instead of
hardcoding memcpy.
* benchtests/bench-memcpy-large.c (test_name): Likewise.
* benchtests/bench-memcpy-random.c (test_name): Likewise.
Print the benchmark output for various memcpy benchmarks in json so
that it can be predictably parsed and analyzed.
* benchtests/bench-memcpy-large.c: Include json-lib.h.
(do_one_test): Print json.
(do_test): Likewise.
(test_main): Likewise.
* benchtests/bench-memcpy-random.c: Include json-lib.h.
(do_one_test): Print json.
(do_test): Likewise.
(test_main): Likewise.
* benchtests/bench-memcpy.c: Include json-lib.h.
(do_one_test): Print json.
(do_test): Likewise.
(test_main): Likewise.
