Intrinsics avaliable in function scope

Add a note when features just enabled in function scope the intrinsics must
be usable.

main/acle.md

@@ -316,6 +316,10 @@ Armv8.4-A [[ARMARMv84]](#ARMARMv84). Support is added for the Dot Product intrin
   * added `FEAT_LS64*`.
 * Added feature detection macro `__ARM_FEATURE_RCPC` for RCpc (Release Consistent processor consistent) model at [RCpc](#rcpc).
 
+#### Changes for next release
+
+* Add intrinsics availability to function scope.
+
 ### References
 
 This document refers to the following documents.
@@ -700,6 +704,15 @@ ACLE standardizes intrinsics to access various features of the
 Arm ® architecture. It also standardizes a set of [header
 files](#header-files) that provide access to these intrinsics.
 
+Availability of a given intrinsics is indicated by the corresponding
+`_ARM_FEATURE_` macro, as detailed in the [Feature test
+macros](#feature-test-macros) section. A given architecture feature could
+be enabled in function scope, for example with the `target` or
+[`target_version`](#function-multi-versioning) attributes. If an
+implementation supports such then the related intrinsics of the enabled
+architecture feature must be available in that scope via the standard
+header files.
+
 Whether intrinsics are macros, functions or built-in operators is
 unspecified. For example: