ed: inferred range commands

[mknos]

• Line addresses can be inferred when entering a range with a comma
• An explicit range has two addresses, e.g. "1,2" or "4,$"
• If first address is not given it is always 1
• If first and last address are both not given, last address is $ (last valid line address)
• I discovered this when testing against OpenBSD and GNU ed
• test1: ",n" --> interpret as 1,$n
• test2: ",5n" --> interpret as 1,5n

[briandfoy]

changes: commands can use inferred line ranges when you omit the first or last value in n,m