Debug Info: Represent macro expansions as inlined functions.

This allows the debugger to choose whether to display the expanded macro
(inlined) or the original source code (parent frame).

rdar://102916513

Author: adrian-prantl

test/Macros/macro_expand.swift

@@ -11,6 +11,9 @@
 // Debug info SIL testing
 // RUN: %target-swift-frontend -emit-sil -enable-experimental-feature Macros -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir %s -module-name MacroUser -o - -g | %FileCheck --check-prefix CHECK-SIL %s
 
+// Debug info IR testing
+// RUN: %target-swift-frontend -emit-ir -enable-experimental-feature Macros -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir %s -module-name MacroUser -o - -g | %FileCheck --check-prefix CHECK-IR %s
+
 // Execution testing
 // RUN: %target-build-swift -g -enable-experimental-feature Macros -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -L %swift-host-lib-dir %s -o %t/main -module-name MacroUser
 // RUN: %target-run %t/main | %FileCheck %s