Adds features to support default file descriptor redirects for the
target process:
1. A new command line flag '--redirect' and '-r' are added to specify
file redirects for the target process
2. New syntax is added to the 'restart' command to specify file
redirects.
3. Interactive instances will check if stdin/stdout and stderr are
terminals and print a helpful error message if they aren't.
Clarify that the currently supported version of the API is 2 and that
the preferred method for selecting it is sending a SetApiVersion
command after connection.
Fixes#2066
* service: also search IPv6 connections when checking user
When checking if the user is allowed to connect to this Delve instance
also search IPv6 connections even though the local address is IPv4.
Fixes#1835
* cmd: add flag to disable same-user check
Fixes#1835
* scripts: use relative path in gen-cli-docs.go
Makes gen-cli-docs.go work outside GOPATH.
* Documentation,cmd/dlv: tidy up --help output
The description of --log-dest, --log-output and --backend is very
verbose and messes up the output of --help, move it to two "additional
help" subcommands.
