Update copyright notice

Remove runtime locks around malloc()/free() in mpmalloc.c for
glibc-based systems.

This is due to following statement in the glibc manual:

   To  avoid  corruption in multithreaded applications,
   mutexes are used internally to protect the memory-management
   data structures employed by these functions. In a multithreaded
   application in which threads simultaneously allocate and free
   memory, there could be contention for these mutexes. To scalably
   handle memory allocation in multithreaded applications,
   glibc creates additional memory  allocation arenas if mutex
   contention is detected.  Each arena is a large region of memory
   that is internally allocated by the system (using brk(2)
   or mmap(2)), and managed with its own mutexes.

Having locks around them in the flang runtime library
can ruin optimization effort when tcmalloc is preloaded
to replace standard malloc()/free() implementation with
the one optimized for reducing lock contention.

Implements pull request #460

Author: gklimowicz

runtime/flangrti/mpmalloc.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, NVIDIA CORPORATION.  All rights reserved.
+ * Copyright (c) 1998-2018, NVIDIA CORPORATION.  All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.