Many of the example loadable builtins don't work anymore

[Emanuele Torre]

Many of the loadable builtins that set variables in the
examples/loadables directory don't work anymore because they still want
to call legal_identifier instead of valid_identifier.

    $ ./bash -c 'enable -f {examples/loadables/,}mktemp; mktemp'
    /tmp/shtmp.h2HpWZ
    $ ./bash -c 'enable -f {examples/loadables/,}mktemp; mktemp -v foo'
    ./bash: symbol lookup error: examples/loadables/mktemp: undefined symbol: 
legal_identifier

Replacing legal_identifier with valid_identifier should resolve the
issue:

    $ git grep -l legal_ examples/loadables
    examples/loadables/asort.c
    examples/loadables/cut.c
    examples/loadables/dsv.c
    examples/loadables/kv.c
    examples/loadables/lcut.c
    examples/loadables/mktemp.c
    examples/loadables/print.c
    examples/loadables/realpath.c
    examples/loadables/stat.c

o/
 emanuele6