Values spanning multiple lines (e.g. a multi-line FORGIT_*_GIT_OPTS
export) were silently dropped: read stopped at the first newline and
IFS only split on spaces, so the resulting array came out empty.
Split on spaces, tabs and newlines and consume the whole value with an
empty delimiter, ignoring leading/trailing whitespace.
Add unit tests covering space-, tab- and newline-separated inputs.
