spi: Make Spi write() work from SWIG with typemaps

This change also changes the C++ API write(char) call to writeByte(uint8_t) and
the write() call now takes a uint8_t* instead of a char*. This should not alter
any code significantly and does not affect the C API.

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

examples/python/spi.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+
+# Author: Brendan Le Foll <brendan.le.foll@intel.com>
+# Copyright (c) 2015 Intel Corporation.
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE
+
+import mraa as m
+import random as rand
+
+# Excuse the super boring example, I was out of fun devices to play with, this
+# will write and read the same data back to itself, a few 100 times, just short
+# MISO & MOSI on your board
+
+dev = m.Spi(0)
+
+for x in range(0,100):
+  txbuf = bytearray(4)
+  for y in range(0,4):
+    txbuf[y] = rand.randrange(0, 256)
+  rxbuf = dev.write(txbuf)
+  if rxbuf != txbuf:
+    print("We have an error captain!")
+    break
+    exit(1)
+