Add KEYCUSTOMFN flag definition and mapping

Added the missing KEYCUSTOMFN keyword flag that was causing compilation errors.

Changes:
- Added KEYCUSTOMFN = 0x10000000 to keyword flags enum in IdentifierTable.h
- Shifted KEYFIXEDPOINT to 0x20000000 to make room
- Added case for KEYCUSTOMFN in getKeywordStatus() in IdentifierTable.cpp
- Maps to LangOpts.CustomizableFunctions

This fixes the 'KEYCUSTOMFN was not declared in this scope' errors.

Author: claude

clang/include/clang/Basic/IdentifierTable.h

@@ -76,7 +76,8 @@ enum TokenKey : unsigned {
   KEYZOS = 0x2000000,
   KEYNOZOS = 0x4000000,
   KEYHLSL = 0x8000000,
-  KEYFIXEDPOINT = 0x10000000,
+  KEYCUSTOMFN = 0x10000000,
+  KEYFIXEDPOINT = 0x20000000,
   KEYMAX = KEYFIXEDPOINT, // The maximum key
   KEYALLCXX = KEYCXX | KEYCXX11 | KEYCXX20,
   KEYALL = (KEYMAX | (KEYMAX - 1)) & ~KEYNOMS18 & ~KEYNOOPENCL &

clang/lib/Basic/IdentifierTable.cpp

@@ -139,6 +139,8 @@ static KeywordStatus getKeywordStatusHelper(const LangOptions &LangOpts,
     return LangOpts.ZVector ? KS_Enabled : KS_Unknown;
   case KEYCOROUTINES:
     return LangOpts.Coroutines ? KS_Enabled : KS_Unknown;
+  case KEYCUSTOMFN:
+    return LangOpts.CustomizableFunctions ? KS_Enabled : KS_Unknown;
   case KEYMODULES:
     return KS_Unknown;
   case KEYOPENCLCXX: