allow_internal_unstable requires feature names

Closes #681 .

library/stdarch/crates/std_detect/src/detect/arch/aarch64.rs

@@ -3,7 +3,7 @@
 /// Checks if `aarch64` feature is enabled.
 #[macro_export]
 #[unstable(feature = "stdsimd", issue = "27731")]
-#[allow_internal_unstable]
+#[allow_internal_unstable(stdsimd_internal)]
 macro_rules! is_aarch64_feature_detected {
     ("neon") => {
         // FIXME: this should be removed once we rename Aarch64 neon to asimd

library/stdarch/crates/std_detect/src/detect/arch/arm.rs

@@ -3,7 +3,7 @@
 /// Checks if `arm` feature is enabled.
 #[macro_export]
 #[unstable(feature = "stdsimd", issue = "27731")]
-#[allow_internal_unstable]
+#[allow_internal_unstable(stdsimd_internal)]
 macro_rules! is_arm_feature_detected {
     ("neon") => {
         cfg!(target_feature = "neon") ||

library/stdarch/crates/std_detect/src/detect/arch/mips.rs

@@ -3,7 +3,7 @@
 /// Checks if `mips` feature is enabled.
 #[macro_export]
 #[unstable(feature = "stdsimd", issue = "27731")]
-#[allow_internal_unstable]
+#[allow_internal_unstable(stdsimd_internal)]
 macro_rules! is_mips_feature_detected {
     ("msa") => {
         cfg!(target_feature = "msa") ||

library/stdarch/crates/std_detect/src/detect/arch/mips64.rs

@@ -3,7 +3,7 @@
 /// Checks if `mips64` feature is enabled.
 #[macro_export]
 #[unstable(feature = "stdsimd", issue = "27731")]
-#[allow_internal_unstable]
+#[allow_internal_unstable(stdsimd_internal)]
 macro_rules! is_mips64_feature_detected {
     ("msa") => {
         cfg!(target_feature = "msa") ||

library/stdarch/crates/std_detect/src/detect/arch/powerpc.rs

@@ -3,7 +3,7 @@
 /// Checks if `powerpc` feature is enabled.
 #[macro_export]
 #[unstable(feature = "stdsimd", issue = "27731")]
-#[allow_internal_unstable]
+#[allow_internal_unstable(stdsimd_internal)]
 macro_rules! is_powerpc_feature_detected {
     ("altivec") => {
         cfg!(target_feature = "altivec") ||

library/stdarch/crates/std_detect/src/detect/arch/powerpc64.rs

@@ -3,7 +3,7 @@
 /// Checks if `powerpc64` feature is enabled.
 #[macro_export]
 #[unstable(feature = "stdsimd", issue = "27731")]
-#[allow_internal_unstable]
+#[allow_internal_unstable(stdsimd_internal)]
 macro_rules! is_powerpc64_feature_detected {
     ("altivec") => {
         cfg!(target_feature = "altivec") ||

library/stdarch/crates/std_detect/src/detect/arch/x86.rs

@@ -79,7 +79,7 @@
 /// [docs]: https://software.intel.com/sites/landingpage/IntrinsicsGuide
 #[macro_export]
 #[stable(feature = "simd_x86", since = "1.27.0")]
-#[allow_internal_unstable]
+#[allow_internal_unstable(stdsimd_internal)]
 macro_rules! is_x86_feature_detected {
     ("aes") => {
         cfg!(target_feature = "aes") || $crate::detect::check_for(