[test] adjust tests for make test VALGRIND=valgrind

result should not interleave with post-exit valgrind ==pid== output
e.g. => "42==16469== Memcheck, a memory error detector"
We need to add "42\n" because ==... is only filtered at new lines.

Some of the filtered valgrind lines are darwin specific:
--$pid:0:syswrap- WARNING: Ignoring sigreturn( ..., UC_RESET_ALT_STACK );
on longjmp, darwin only.
or UNKNOWN task message [id 3403, to mach_task_self(), reply 0x813]

Closes GH #1150
[test] refactor, new valgrind_filter function

also print LEAK SUMMARY: definitely lost: $1 bytes in $2 blocks
if so. GH #1150
[embed] add some missing embed methods GH #829

fails with an encoding assertion in str_new_init
change extend.t: 15 extend-style compile_string + call
remove imcc/api.h from embed api test
[embed] more extend tuning, fix compile_string

use dynamic STRINGs, not constant, and not char*.
Also honor TEST_VERBOSE=2 in c_output_is
[extend] special case ext_call "->"

might be a worthwile optimization. however:
16.589294527 0.13% => 16.612686915 0.21% on parrot-bench linux
similar on darwin, but darwin bench is more noisy
[extend] remove comment for Parrot_get_root_namespace

failed bad t/codingstd/c_arg_assert.t test