Clean up.

Clean up.
* src/scan-skel.l (at_directive_perform): Add at_directive_argc and
at_directive_argv arguments so these no longer have to be global
variables.  Also, update the implementation for the following changes.
(fail_for_at_directive_too_many_args,
fail_for_at_directive_too_few_args): Add at_directive_name argument.
(at_directive_name): Remove as at_directive_argv[0] will be used for
this now.
(AT_DIRECTIVE_ARGC_MAX): Increment to make space in at_directive_argv
for the directive name.
(at_directive_argc, at_directive_argv): Make these local within
skel_lex instead of global.
(INITIAL): Update directive start action for above changes.
(SC_AT_DIRECTIVE_ARG): Rename to...
(SC_AT_DIRECTIVE_ARGS): ... this, and update for above changes.
(SC_AT_DIRECTIVE_SKIP_WS): Update.
(scan_skel): Move yylex_destroy to...
(skel_scanner_free): ... here.
* tests/skeletons.at (installed skeleton file name): Rename to...
(installed skeleton file names): ... this.