This commit fixes rights check for `fd_pread` and `fd_pwrite` to be conformant with the WASI spec. In the spec, it is clearly stated that the right to invoke `__wasi_fd_pread()` requires a combination of `__WASI_RIGHT_FD_READ` with `__WASI_RIGHT_FD_SEEK`, and similarly for `__wasi_fd_pwrite()` the combination is `__WASI_RIGHT_FD_WRITE` with `__WASI_RIGHT_FD_SEEK`. Relevant link to the spec: [__wasi_rights_t]. [__wasi_rights_t]: https://github.com/WebAssembly/WASI/blob/master/phases/snapshot/docs/wasi_unstable_preview1.md#__wasi_rights_t-uint64_t-bitfield
This is the wasi-tests crate, which contains source code for the system-level WASI tests.
Building these tests requires that the wasm32-wasi target be installed.