[binutils-gdb] Update help text in record.c

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT a974b5ec9a253d330290d132098065b77f29bd36 ***

Author: Tom Tromey <tom@tromey.com>
Branch: master
Commit: a974b5ec9a253d330290d132098065b77f29bd36

Update help text in record.c

This updates some help text in record.c to conform to GNU standards.
I also added a "Usage" line to "record save".

2018-04-29  Tom Tromey  <tom@tromey.com>

	* record.c (_initialize_record): Update help text.