Add copyright notices to long-enough files that lack them, since

Add copyright notices to long-enough files that lack them, since
otherwise the files aren't clearly free.  Use the same notice that
getdate.texi already uses.
* doc/alloca-opt.texi: Add copyright notice.
* doc/alloca.texi: Likewise.
* doc/ctime.texi: Likewise.
* doc/functions.texi: Likewise.
* doc/gcd.texi: Likewise.
* doc/gnulib-tool.texi: Likewise.
* doc/inet_ntoa.texi: Likewise.
* doc/visibility.texi: Likewise.

Change copyright notice from LGPL 2 to GPL 2, since that's the
standard form used in the gnulib repository.
* lib/lock.c: LGPL -> GPL.
* lib/lock.h: Likewise.
* lib/strnlen1.c: Likewise.
* lib/strnlen1.h: Likewise.
* lib/tls.c: Likewise.
* lib/tls.h: Likewise.
* lib/tmpdir.c: Likewise.
* tests/test-lock.c: Likewise.
* tests/test-stdint.c: Likewise.
* tests/test-tls.c: Likewise.