Specifying the lower boundary suffixed by colon is an undocumented
feature. Explicitly printing the upper boundary in that case seems sane.
Signed-off-by: Phil Sutter <phil@nwl.cc>
-m length --length 1;=;OK
-m length --length :2;-m length --length 0:2;OK
-m length --length 0:3;=;OK
--m length --length 4:;=;OK
+-m length --length 4:;-m length --length 4:65535;OK
-m length --length 0:65535;=;OK
-m length ! --length 0:65535;=;OK
-m length --length 0:65536;;FAIL