line-log: mention both modes in 'blame' and 'log' short help

line-log: mention both modes in 'blame' and 'log' short help

'git blame -h' and 'git log -h' both show '-L <n,m>' and describe this
option as "Process only line range n,m, counting from 1". No hint is
given that a function name regex can also be used.

Use <range> instead, and expand the description of the option to mention
both modes. Remove "counting from 1" as it's uneeded; it's uncommon to
refer to the first line of a file as "line 0".

Also, for 'git log', improve the wording to better reflect the long help.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>