Increase maximum input buffer

macOS' built in VNC server unfortunately sends the entire monitor in a
single rect, so we need to be prepared to buffer a lot of data in case
the monitor has a large resolution.

(cherry picked from commit 479ec11a2e)

common/rdr/BufferedInStream.cxx

@@ -27,7 +27,7 @@
 using namespace rdr;
 
 static const size_t DEFAULT_BUF_SIZE = 8192;
-static const size_t MAX_BUF_SIZE = 4 * 1024 * 1024;
+static const size_t MAX_BUF_SIZE = 32 * 1024 * 1024;
 
 BufferedInStream::BufferedInStream()
   : bufSize(DEFAULT_BUF_SIZE), offset(0)