mailmap: do not lose single-letter names

mailmap: do not lose single-letter names

In parse_name_and_email() function, there is this line:

	*name = (nstart < nend ? nstart : NULL);

When the function is given a buffer "A <A@example.org> <old@x.z>",
nstart scans from the beginning of the buffer, skipping whitespaces
(there isn't any, so nstart points at the buffer), while nend starts
from one byte before the first '<' and skips whitespaces backwards
and stops at the first non-whitespace (i.e. it hits "A" at the
beginning of the buffer).  nstart == nend in this case for a
single-letter name, and an off-by-one error makes it fail to pick up
the name, which makes the entry equivalent to

	<A@example.org> <old@x.z>

without the name.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>