Add support for AArch32

gcc version 4.9.2 (Raspbian 4.9.2-10)
Tested on Linux raspberrypi 4.4.6-v7+ #875 SMP Tue Apr 12 16:33:02 BST 2016 armv7l GNU/Linux

CPUs may be little or big endian, detect with gcc flags, not the processor architecture
Add a new flag $(PLATFORM)_uses_openssl which allows to disable the link with openssl lib.

vlib/vlib/threads.c:
startup.conf must:
- specify the heapsize as we don't have hugepages on raspbian

cpu {
  main-core 3
}
heapsize 64M

Corrects in various files the assumption uword == u64 and replaces 'u64' cast with 'pointer_to_uword' and 'uword_to_pointer' where appropriate.
256 CPUs may create an OOM when testing with small memory footprint ( heapsize 64M ), allows the number of VLIB_MAX_CPUS to be set in platforms/*.mk

vppinfra/vppinfra/longjmp.S:
ARM - copy r1 (1st parameter of the setjmp call) to r0 (return value)

vppinfra/vppinfra/time.h:
On ARMv7 in AArch32 mode, we can access to a 64bit register to retreive the cycles count.
gcc on rpi only declare ARM_ARCH 6. Override this info, and check if it is possible to use 'mrrc'.
/!\ the time function will NOT work without allowing the user mode access to the PMU.
You may download the source of the kmod here:
https://github.com/christophefontaine/arm_rdtsc

Change-Id: I8142606436d9671a184133b935398427f08a8bd2
Signed-off-by: Christophe Fontaine <christophe.fontaine@qosmos.com>
diff --git a/vlib-api/vlibmemory/memory_vlib.c b/vlib-api/vlibmemory/memory_vlib.c
index 7ba76ec..107fddc 100644
--- a/vlib-api/vlibmemory/memory_vlib.c
+++ b/vlib-api/vlibmemory/memory_vlib.c
@@ -1135,8 +1135,8 @@
       if (mp->need_barrier_sync)
         vlib_worker_thread_barrier_sync (vm);
 
-      fp = (void *)(mp->function);
-      rv = (*fp)(mp->data);
+      fp = uword_to_pointer(mp->function, int(*)(void *));
+      rv = fp(mp->data);
 
       if (mp->need_barrier_sync)
         vlib_worker_thread_barrier_release (vm);
@@ -1174,7 +1174,7 @@
   memset (mp, 0, sizeof (*mp));
   memcpy (mp->data, data, data_length);
   mp->_vl_msg_id = ntohs (VL_API_RPC_CALL);
-  mp->function = (u64)fp;
+  mp->function = pointer_to_uword(fp);
   mp->need_barrier_sync = 1;
   
   /* Use the "normal" control-plane mechanism for the main thread */