Atomics

Fixed:
- Properly pin `patomic` version to `v0.2.2` even if `patomic` has a stable
release (which it now does)

Changed
- freeze default `patomic` version to `v0.2.2` until `patomic` has a stable
release (to allow for breaking changes in `devel` branch)

Added
- Verbosity now obtained from `-v`/`-verbose` flags (removed `-log-level` flag)
- Added `-linker-args` flag to user options (with `-l` as shortcut)
Removed
- `-log-level` option
Changed
- `-l` is now `-linker-args` rather than `log-level`
Fixed:
- Filled in missing details in `setup.cfg` for older build systems:
- Specified `build-backend` option as `setuptools.build_meta`
- Added `install_requires` and `setup_requires`
- `cmake_args` option in `build_patomic` command now actually used

Added
- Initial release
- Implementation is Python wrapper around `patomic` C library
- Provides:
- **.**: `atomic()`, `atomicview()`
- **.**: `Alignment`, `CmpxchgResult`, `MemoryOrder`, `OpType`
- **.**: `ANY`, `INTEGRAL`, `BYTES`, `INT`, `UINT`
- **.base**: `Atomic`, `Atomic{Integral|Bytes|Int|Uint}`
- **.view**: `AtomicView`, `Atomic{Integral|Bytes|Int|Uint}View`
- **.ctx**: `AtomicViewContext`, `Atomic{Integral|Bytes|Int|Uint}ViewContext`
- **.exc**: `AlignmentError`, `MemoryOrderError`,
`Unsupported{Width|Operation}Exception`
- Cmpxchg functions return `CmpxchgResult[T]` (with `T` in `[bytes, int]`)
- No testing provided