Exposes new c-api functions for configuring relaxed SIMD (#6292)

* Exposes new c-api functions for configuring relaxed SIMD:

 - wasmtime_config_wasm_relaxed_simd_set(bool)
 - wasmtime_config_wasm_relaxed_simd_deterministic_set(bool)

* Applied rustfmt suggestion

* Added header file entries for new calls

* Fixed link to `relaxed simd proposal`

Author: martindevans

crates/c-api/include/wasmtime/config.h

@@ -165,6 +165,22 @@ WASMTIME_CONFIG_PROP(void, wasm_reference_types, bool)
  */
 WASMTIME_CONFIG_PROP(void, wasm_simd, bool)
 
+/**
+ * \brief Configures whether the WebAssembly relaxed SIMD proposal is
+ * enabled.
+ *
+ * This setting is `false` by default.
+ */
+WASMTIME_CONFIG_PROP(void, wasm_relaxed_simd, bool)
+
+/**
+ * \brief Configures whether the WebAssembly relaxed SIMD proposal is
+ * in deterministic mode.
+ *
+ * This setting is `false` by default.
+ */
+WASMTIME_CONFIG_PROP(void, wasm_relaxed_simd_deterministic, bool)
+
 /**
  * \brief Configures whether the WebAssembly bulk memory proposal is
  * enabled.

crates/c-api/src/config.rs

@@ -81,6 +81,19 @@ pub extern "C" fn wasmtime_config_wasm_simd_set(c: &mut wasm_config_t, enable: b
     c.config.wasm_simd(enable);
 }
 
+#[no_mangle]
+pub extern "C" fn wasmtime_config_wasm_relaxed_simd_set(c: &mut wasm_config_t, enable: bool) {
+    c.config.wasm_relaxed_simd(enable);
+}
+
+#[no_mangle]
+pub extern "C" fn wasmtime_config_wasm_relaxed_simd_deterministic_set(
+    c: &mut wasm_config_t,
+    enable: bool,
+) {
+    c.config.relaxed_simd_deterministic(enable);
+}
+
 #[no_mangle]
 pub extern "C" fn wasmtime_config_wasm_bulk_memory_set(c: &mut wasm_config_t, enable: bool) {
     c.config.wasm_bulk_memory(enable);

crates/wasmtime/src/config.rs

@@ -666,8 +666,7 @@ impl Config {
     ///
     /// The [WebAssembly SIMD proposal][proposal]. This feature gates items such
     /// as the `v128` type and all of its operators being in a module. Note that
-    /// this does not enable the [relaxed simd proposal] as that is not
-    /// implemented in Wasmtime at this time.
+    /// this does not enable the [relaxed simd proposal].
     ///
     /// On x86_64 platforms note that enabling this feature requires SSE 4.2 and
     /// below to be available on the target platform. Compilation will fail if