llvm: Fix file-ending in IDENTIFICATION comments.

Author: Amit Langote
Discussion: https://postgr.es/m/9a54dcef-c799-ce89-2e47-0a7fc12d5fc2@lab.ntt.co.jp
Backpatch: 11-, where llvm was introduced.

src/backend/jit/llvm/llvmjit_error.cpp

@@ -9,7 +9,7 @@
  * Copyright (c) 2016-2019, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  src/backend/jit/llvm/llvmjit_error.c
+ *	  src/backend/jit/llvm/llvmjit_error.cpp
  *
  *-------------------------------------------------------------------------
  */

src/backend/jit/llvm/llvmjit_inline.cpp

@@ -14,7 +14,7 @@
  * Copyright (c) 2016-2019, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  src/backend/lib/llvmjit/llvmjit_inline.c
+ *	  src/backend/lib/llvmjit/llvmjit_inline.cpp
  *
  *-------------------------------------------------------------------------
  */

src/backend/jit/llvm/llvmjit_wrap.cpp

@@ -6,7 +6,7 @@
  * Copyright (c) 2016-2019, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  src/backend/lib/llvm/llvmjit_wrap.c
+ *	  src/backend/lib/llvm/llvmjit_wrap.cpp
  *
  *-------------------------------------------------------------------------
  */