Fix a compilation with non-clang/non-gcc compilers

source/common/putilimp.h

 /*
 ******************************************************************************
 *
 *   Copyright (C) 1997-2015, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *
 ******************************************************************************
 *
 *  FILE NAME : putilimp.h
 *
@@ skipping 218 matching lines @@
 #endif
 
 
 /**
  *  \def U_HAVE_CLANG_ATOMICS
  *  Defines whether Clang c11 style built-in atomics are avaialable.
  *  These are used in preference to gcc atomics when both are available.
  */
 #ifdef U_HAVE_CLANG_ATOMICS
     /* Use the predefined value. */
-#elif defined(__clang__) && \
-      __has_builtin(__c11_atomic_load) && \
-      __has_builtin(__c11_atomic_store) && \
-      __has_builtin(__c11_atomic_fetch_add) && \
-      __has_builtin(__c11_atomic_fetch_sub)
+#elif !defined(__clang__)
+#    define U_HAVE_CLANG_ATOMICS 0
+#else
+#if __has_builtin(__c11_atomic_load) && \
+    __has_builtin(__c11_atomic_store) && \
+    __has_builtin(__c11_atomic_fetch_add) && \
+    __has_builtin(__c11_atomic_fetch_sub)
 #    define U_HAVE_CLANG_ATOMICS 1
 #else
 #    define U_HAVE_CLANG_ATOMICS 0
 #endif
+#endif
 
 /*===========================================================================*/
 /** @{ Code alignment                                                        */
 /*===========================================================================*/
 
 /**
  * \def U_ALIGN_CODE
  * This is used to align code fragments to a specific byte boundary.
  * This is useful for getting consistent performance test results.
  * @internal
@@ skipping 367 matching lines @@
 /* also _C_TS_calloc(x) */
 #else
 /* C defaults */
 # define uprv_default_malloc(x) malloc(x)
 # define uprv_default_realloc(x,y) realloc(x,y)
 # define uprv_default_free(x) free(x)
 #endif
 
 
 #endif