Fix clang errors

Make clang build without errors in the async code
Reviewed-by: NRich Salz <rsalz@openssl.org>

crypto/async/arch/async_posix.c

@@ -65,9 +65,12 @@ __thread async_ctx *sysvctx;
 
 #define STACKSIZE       32768
 
-__thread size_t pool_max_size = 0;
-__thread size_t pool_curr_size = 0;
-__thread STACK_OF(ASYNC_JOB) *pool = NULL;
+extern __thread size_t posixpool_max_size;
+extern __thread size_t posixpool_curr_size;
+extern __thread STACK_OF(ASYNC_JOB) *posixpool;
+__thread size_t posixpool_max_size = 0;
+__thread size_t posixpool_curr_size = 0;
+__thread STACK_OF(ASYNC_JOB) *posixpool = NULL;
 
 int async_fibre_init(async_fibre *fibre)
 {
@@ -117,42 +120,43 @@ int async_read1(int fd, void *buf)
 
 STACK_OF(ASYNC_JOB) *async_get_pool(void)
 {
-    return pool;
+    return posixpool;
 }
 
 int async_set_pool(STACK_OF(ASYNC_JOB) *poolin, size_t curr_size,
                     size_t max_size)
 {
-    pool = poolin;
-    pool_curr_size = curr_size;
-    pool_max_size = max_size;
+    posixpool = poolin;
+    posixpool_curr_size = curr_size;
+    posixpool_max_size = max_size;
     return 1;
 }
 
 void async_increment_pool_size(void)
 {
-    pool_curr_size++;
+    posixpool_curr_size++;
 }
 
 void async_release_job_to_pool(ASYNC_JOB *job)
 {
-    sk_ASYNC_JOB_push(pool, job);
+    sk_ASYNC_JOB_push(posixpool, job);
 }
 
 size_t async_pool_max_size(void)
 {
-    return pool_max_size;
+    return posixpool_max_size;
 }
 
 void async_release_pool(void)
 {
-    sk_ASYNC_JOB_free(pool);
-    pool = NULL;
+    sk_ASYNC_JOB_free(posixpool);
+    posixpool = NULL;
 }
 
 int async_pool_can_grow(void)
 {
-    return (pool_max_size == 0) || (pool_curr_size < pool_max_size);
+    return (posixpool_max_size == 0)
+        || (posixpool_curr_size < posixpool_max_size);
 }
 
 #endif