liblzma: Avoid a warning about a shadowed variable.

On Mac OS X wait() is declared in <sys/wait.h> that
we include one way or other so don't use "wait" as
a variable name.

Thanks to Christian Kujau.
diff --git a/src/liblzma/common/stream_encoder_mt.c b/src/liblzma/common/stream_encoder_mt.c
index cd7b291..f9bd6a1 100644
--- a/src/liblzma/common/stream_encoder_mt.c
+++ b/src/liblzma/common/stream_encoder_mt.c
@@ -420,7 +420,7 @@
 
 /// Make the threads stop but not exit. Optionally wait for them to stop.
 static void
-threads_stop(lzma_coder *coder, bool wait)
+threads_stop(lzma_coder *coder, bool wait_for_threads)
 {
 	// Tell the threads to stop.
 	for (uint32_t i = 0; i < coder->threads_initialized; ++i) {
@@ -430,7 +430,7 @@
 		}
 	}
 
-	if (!wait)
+	if (!wait_for_threads)
 		return;
 
 	// Wait for the threads to settle in the idle state.