pwm.hpp: Add C++ wrapper around Pwm

* maa_pwm_context becomes an opaque pointer
* C++ wrapper class Pwm
* swig now uses C++ wrapper Pwm to generate API

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

examples/cycle-pwm3.c

@@ -30,7 +30,7 @@ int
 main ()
 {
     maa_init();
-    maa_pwm_context* pwm;
+    maa_pwm_context pwm;
     pwm = maa_pwm_init(3);
     if (pwm == NULL) {
         return 1;