getgrent(3) manual page lies

[utzoo!henry]

The manual page getgrent(3) claims that getgrent, getgrgid, and getgrnam
all work from the current location in the file.  This is wrong.  They work
just like the corresponding getpwent(3) routines:  getgrgid and getgrnam start
at the beginning of the file regardless.  The last two paragraphs of the
DESCRIPTION section of getgrent(3) should read like the same two in the
getpwent(3) page.