Rename MAX_BUFFER_SIZE

MAX_BUFFER_SIZE, which is used for limiting the amount of the data
read from a socket renamed to MXS_MAX_NW_READ_BUFFER_SIZE and moved
from gw.h to limits.h.

Consider removing altogether. Difficult to justify since non-blocking
reads are used and the amount of available data is known.

include/maxscale/gw.h

@@ -38,9 +38,6 @@
 
 MXS_BEGIN_DECLS
 
-// network buffer is 32K
-#define MAX_BUFFER_SIZE 32768
-
 #define GW_NOINTR_CALL(A)       do { errno = 0; A; } while (errno == EINTR)
 
 bool gw_daemonize(void);

include/maxscale/limits.h

@@ -33,7 +33,7 @@ MXS_BEGIN_DECLS
 #define MXS_BACKEND_SO_RCVBUF (128 * 1024)
 
 /**
- * MSX_BACKEND_SO_SNDBUF
+ * MXS_BACKEND_SO_SNDBUF
  *
  * The value used when setting SO_SNDBUF of backend sockets.
  */
@@ -53,6 +53,16 @@ MXS_BEGIN_DECLS
  */
 #define MXS_CLIENT_SO_SNDBUF  (128 * 1024)
 
+/**
+ * MXS_MAX_NW_READ_BUFFER_SIZE
+ *
+ * The maximum amount of data read in one gofrom a client DCB.
+ *
+ * TODO: Consider removing altogether so that we always read
+ *       whatever is available in the socket.
+ */
+#define MXS_MAX_NW_READ_BUFFER_SIZE (32 * 1024)
+
 /**
  * MXS_MAX_THREADS
  *