Fix test and improve dumper

Author: DougGregor

lib/AST/AvailabilityContext.cpp

@@ -241,6 +241,9 @@ void AvailabilityContext::print(llvm::raw_ostream &os) const {
 
   if (isDeprecated())
     os << " deprecated";
+
+  if (allowsUnsafe())
+    os << " allows_unsafe";
 }
 
 void AvailabilityContext::dump() const { print(llvm::errs()); }

test/Interop/Cxx/class/safe-interop-mode.swift

@@ -55,16 +55,20 @@ struct MyContainer {
 import Test
 import CoreFoundation
 
+// expected-note@+1{{mark the enclosing global function 'useUnsafeParam' '@unsafe' to allow it to use unsafe constructs}}{{1-1=@unsafe }}
 func useUnsafeParam(x: Unannotated) { // expected-warning{{reference to unsafe struct 'Unannotated'}}
 }
 
+// expected-note@+2{{mark the enclosing global function 'useUnsafeParam2' '@unsafe' to allow it to use unsafe constructs}}{{10:1-1=@unsafe }}
 @available(SwiftStdlib 5.8, *)
 func useUnsafeParam2(x: UnsafeReference) { // expected-warning{{reference to unsafe class 'UnsafeReference'}}
 }
 
+// expected-note@+1{{mark the enclosing global function 'useUnsafeParam3' '@unsafe' to allow it to use unsafe constructs}}{{1-1=@unsafe }}
 func useUnsafeParam3(x: UnknownEscapabilityAggregate) { // expected-warning{{reference to unsafe struct 'UnknownEscapabilityAggregate'}}
 }
 
+// expected-note@+1{{mark the enclosing global function 'useSafeParams' '@unsafe' to allow it to use unsafe constructs}}{{1-1=@unsafe }}
 func useSafeParams(x: Owner, y: View, z: SafeEscapableAggregate, c: MyContainer) {
     let _ = c.__beginUnsafe() // expected-warning{{call to unsafe instance method '__beginUnsafe'}}
 }