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.
In the Subversion libraries, replace uses of "assert" and "abort" with the new SVN_ERR_ASSERT and SVN_ERR_MALFUNCTION macros where possible. Replace "if (cond) abort();" with "SVN_ERR_ASSERT(!cond)".
This is a like-for-like change except that the new macros allow the application at run time to specify an alternative behaviour such as returning an error object instead of aborting, and they are not affected by the NDEBUG macro (so they are not compiled out in release-mode builds as "assert" could be).
Omit libsvn_ra_serf because it uses assert and abort as placeholders for unfinished development.