shells/rc: Update to 1.7.4, Fix build

[dbaio]

Summary

shells/rc: Update to 1.7.4, Fix build

After ports r440197, there is a build problem with the default option.

- Update to 1.7.4 and fix build
- Move MASTER_SITES to the currently upstream address
- Improve pkg-descr
- Set LICENSE

PR:	219596
Approved by:	garga (mentor), maintainer (timeout)
Differential Revision:	https://reviews.freebsd.org/D11126

Test Plan

$ portlint -C
looks fine.

poudriere testport (default option):

10.3-RELEASE-p19 amd64
10.3-RELEASE-p19 i386
11.0-RELEASE-p10 amd64
11.0-RELEASE-p10 i386
12.0-CURRENT 1200031 amd64
12.0-CURRENT 1200031 i386

poudriere testport (with READLINE):

10.3-RELEASE-p19 amd64
10.3-RELEASE-p19 i386
11.0-RELEASE-p10 amd64
11.0-RELEASE-p10 i386
12.0-CURRENT 1200031 amd64
12.0-CURRENT 1200031 i386