VPP-118: add support for variable length arrays to jvpp

* extends VPP's message definition language with the following syntax:

u32 count:
u8 array[count];

which is traslated to:

u32 count;
u8 array[0];

but now, python API representation generated by vppapigen
contains information about where the array length is stored.

* modifies existing response messages to use the new syntax

Change-Id: I68210bc7a3a755d03d067e9b79a567f40e2d31f3
Signed-off-by: Marek Gradzki <mgradzki@cisco.com>

vpp-api/python/pneum/api-gen.py

@@ -67,7 +67,7 @@ def get_pack(t):
     j = -1
     for i in t:
         j += 1
-        if len(i) is 3:
+        if len(i) is 3 or len(i) is 4:  # TODO: add support for variable length arrays (VPP-162)
             size = type_size[i[0]]
             bytecount += size * int(i[2])
             # Check if we have a zero length array