Relicense Subversion under the Apache License, Version 2.0.
* NOTICE: New.
* LICENSE: New.
* COPYING, subversion/LICENSE: Remove.
* subversion/libsvn_subr/opt.c (svn_opt__print_version_info): Note that the product as a whole is copyrighted by the SVN Corp, and that it contains contributions from many people, as referenced in NOTICE.
* subversion/bindings/swig/python/LICENSE_FOR_PYTHON_BINDINGS: Relicense the SVN parts under Apache 2.0.
* everywhere: Change copyright notices in file headers to reflect the Apache 2.0 license.
Sprinkle some const-correctness on the unidiff application code.
Suggested by: gstein
* subversion/libsvn_client/patch.c (patch_target_t): Mark two fields const. (apply_textdiffs, init_patch_target, determine_hunk_line, merge_hunk, apply_one_hunk, maybe_send_patch_target_notification, apply_one_patch): Mark some parameters const.