Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
The thrift compiler (since 0.13 at least) complains that
the csharp target is deprecated and recommend replacing it
with netstd. Since we don't use either, humor it.
I suspect that this warning caused some spurious rebuilds,
but have not proven it.
org::apache::cassandra (the generated namespace name) gets confused with
apache::cassandra (the thrift runtime library namespace), either due to
changes in gcc 7 or in thrift 0.10. Either way, the problem is fixed
by changing the generated namespace to plain cassandra.
The generic thrift headers bring in a #define (yuch) named VERSION, while the
Cassandra interface also defines a symbol with the same name.
Rename the symbol to avoid a compile conflict.
