* m4/javacomp.m4 (gt_JAVACOMP): Use option '-Xlint:-options' by default
and omit it only when it does not work.
* lib/javacomp.c (compile_using_javac): Add nowarn_option parameter.
(is_envjavac_usable): Add nowarn_option_out parameter. Use option
'-Xlint:-options' by default and omit it only when it does not work.
(is_javac_usable): Likewise.
(compile_java_class): Store the nowarn_option returned from
is_envjavac_usable and use it when invoking compile_using_envjavac.
Store the nowarn_option returned from is_javac_usable and use it when
invoking compile_using_javac.