This patch switches code to SPDX one-line license identifiers according to
https://spdx.dev/learn/handling-license-info/
and replacing long license text headers.
I used C++ format on the first line in style
// SPDX-License-Identifier: <id>
except exported libcryptsetup.h, when only C comments are used.
The only additional changes are:
- switch backend utf8.c from LGPL2+ to LGPL2.1+ (as in systemd)
- add some additional formatting lines.
Atomic operation requires to hold a lock for longer period than
single metadata I/O. Update locks so that we can:
- lock a device more than once (lock ref counting)
- reaquire read lock on already held write lock (write lock
is stronger than read lock)
