rs, sys: mention new feature flags in README

Author: jiegec

README.md

@@ -122,6 +122,10 @@ More complex demos welcome!
   [`Error` trait](https://doc.rust-lang.org/std/error/trait.Error.html)
 - `use_bindgen`: run `bindgen` to generate Rust bindings to Capstone C library
   instead of using pre-generated bindings (not recommended).
+- `arch_$ARCH`<sup>&dagger;</sup>: enable arch `$ARCH` support in capstone,
+  e.g. `arch_arm64` enables arch arm64 support.
+- `support_all_archs`<sup>&dagger;</sup>: enable all archs available
+  in capstone, imply all `arch_$ARCH` features.
 
 <sup>&dagger;</sup>: enabled by default
 

capstone-sys/README.md

@@ -24,5 +24,8 @@ Instead, consider using [capstone-rs](https://github.com/capstone-rust/capstone-
 
 You can specify the following [features](https://doc.rust-lang.org/cargo/reference/manifest.html#the-features-section) in `Cargo.toml`:
 * `use_bindgen`: instead of using the pre-generated Capstone bindings, dynamically generate bindings with [`bindgen`][bindgen].
+* `full` (enabled by default): enable full capstone build instead of diet.
+* `arch_$ARCH` (enabled by default): enable arch `$ARCH` support in capstone, e.g. `arch_arm64` enables arch arm64 support.
+* `support_all_archs` (enabled by default): enable all archs available in capstone, imply all `arch_$ARCH` features.
 
 [bindgen]: https://github.com/rust-lang-nursery/rust-bindgen