r19343: Add support for external scripts/binaries that write results using the

r19343: Add support for external scripts/binaries that write results using the
'subunit' protocol. This allows us to easily plug EJS scripts or binaries that
can't depend on -ltorture into smbtorture. The protocol is very simple:

- write "comments" to stderr

Example output on stdout:
test: foo
success: foo
test: bar
success: bar
test: blah
failure: blah [
dummy.c:30: Expression 1 != 2 failed!
]
test: blie
skip: blie [
Iconv support not built in
]

I've already converted the talloc testsuite.
(This used to be commit e1742c14a247fabba969f8698108e73997d3f420)