Update Xcode support for C23

Author: cdervis

features_c23.yaml

@@ -6,25 +6,25 @@ features:
       - GCC 9
       - Clang 9
       - MSVC
-      - Xcode ?
+      - Xcode 11.4
   - desc: "`[[nodiscard]]`"
     paper: N2267
     support:
       - GCC 10
       - Clang 9
-      - Xcode ?
+      - Xcode 11.4
   - desc: "`[[maybe_unused]]`"
     paper: N2270
     support:
       - GCC 10
       - Clang 9
-      - Xcode ?
+      - Xcode 11.4
   - desc: "`[[deprecated]]`"
     paper: N2334
     support:
       - GCC 10
       - Clang 9
-      - Xcode ?
+      - Xcode 11.4
   - desc: "[Attributes](https://en.cppreference.com/w/c/language/attributes.html)"
     paper:
       - N2335
@@ -33,7 +33,7 @@ features:
     support:
       - GCC 10
       - Clang 9
-      - Xcode ?
+      - Xcode 11.4
   - desc: "IEEE 754 decimal floating-point types"
     paper: N2341
     support:
@@ -44,7 +44,7 @@ features:
     support:
       - GCC 10
       - Clang 9
-      - Xcode ?
+      - Xcode 11.4
   - desc: "[u8 character constants](https://en.cppreference.com/w/c/language/character_constant.html)"
     paper: N2418
     support:
@@ -89,7 +89,8 @@ features:
       - Clang 2.9 (hint)
       - Clang 9
       - MSVC 14.0 (hint)
-      - Xcode ?
+      - Xcode (hint)
+      - Xcode 11.4
       - owcc
       - TinyCC
     hints:
@@ -99,18 +100,20 @@ features:
         msg: "Supported as an extension."
       - target: MSVC 14.0
         msg: "Supported as an extension."
+      - target: Xcode
+        msg: "Supported as an extension."
   - desc: "[__has_c_attribute](https://en.cppreference.com/w/c/language/attributes.html#Attribute_testing) in preprocessor conditionals"
     paper: N2553
     support:
       - GCC 11
       - Clang 9
-      - Xcode ?
+      - Xcode 11.4
   - desc: "Allow duplicate attributes"
     paper: N2557
     support:
       - GCC 11
       - Clang 13
-      - Xcode ?
+      - Xcode 11.4
   - desc: "IEEE 754 interchange and extended types"
     paper: N2601
     support:
@@ -137,7 +140,7 @@ features:
       - GCC 12
       - Clang 13
       - MSVC 14.0 (hint)
-      - Xcode ?
+      - Xcode 13.4
     hints:
       - target: MSVC 14.0
         msg: "Supported as an extension."
@@ -203,7 +206,7 @@ features:
       - GCC 5
       - Clang
       - MSVC 14.11
-      - Xcode ?
+      - Xcode
       - TinyCC
   - desc: "Identifier Syntax using Unicode Standard Annex 31"
     paper: N2836