[OpenCL] Pretty print __private addr space

Add printing of __private address space to TypePrinter to allow
it appears in diagnostics and AST dumps as all other language
addr spaces.

Tags: #clang

Differential Revision: https://reviews.llvm.org/D71272
diff --git a/clang/test/SemaOpenCL/null_queue.cl b/clang/test/SemaOpenCL/null_queue.cl
index 34d1a62..a0b33d4 100644
--- a/clang/test/SemaOpenCL/null_queue.cl
+++ b/clang/test/SemaOpenCL/null_queue.cl
@@ -4,13 +4,13 @@
 void queue_arg(queue_t); // expected-note {{passing argument to parameter here}}
 
 void init() {
-  queue_t q1 = 1; // expected-error{{initializing 'queue_t' with an expression of incompatible type 'int'}}
+  queue_t q1 = 1; // expected-error{{initializing '__private queue_t' with an expression of incompatible type 'int'}}
   queue_t q = 0;
 }
 
 void assign() {
   queue_t q2, q3;
-  q2 = 5; // expected-error{{assigning to 'queue_t' from incompatible type 'int'}}
+  q2 = 5; // expected-error{{assigning to '__private queue_t' from incompatible type 'int'}}
   q3 = 0;
   q2 = q3 = 0;
 }
@@ -21,7 +21,7 @@
          get_default_queue() == 1 && // expected-error{{invalid operands to binary expression ('queue_t' and 'int')}}
 	     q4 == q5 &&
 	     q4 != 0 &&
-	     q4 != 0.0f; // expected-error{{invalid operands to binary expression ('queue_t' and 'float')}}
+	     q4 != 0.0f; // expected-error{{invalid operands to binary expression ('__private queue_t' and 'float')}}
 }
 
 void call() {