Update inflateBack() comments, since inflate() can be faster.

zlib.h

@@ -1031,11 +1031,12 @@ ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,
                                     out_func out, void FAR *out_desc));
 /*
      inflateBack() does a raw inflate with a single call using a call-back
-   interface for input and output.  This is more efficient than inflate() for
-   file i/o applications in that it avoids copying between the output and the
-   sliding window by simply making the window itself the output buffer.  This
-   function trusts the application to not change the output buffer passed by
-   the output function, at least until inflateBack() returns.
+   interface for input and output.  This is potentially more efficient than
+   inflate() for file i/o applications, in that it avoids copying between the
+   output and the sliding window by simply making the window itself the output
+   buffer.  inflate() can be faster on modern CPUs when used with large
+   buffers.  inflateBack() trusts the application to not change the output
+   buffer passed by the output function, at least until inflateBack() returns.
 
      inflateBackInit() must be called first to allocate the internal state
    and to initialize the state with the user-provided window buffer.