fix for warnings from Sparse static source code checker, mostly BKE/BLI and python functions.

- use NULL rather then 0 where possible (makes code & function calls more readable IMHO).
- set static variables and functions (exposed some unused vars/funcs).
- use func(void) rather then func() for definitions.

source/blender/python/intern/bpy_util.c

@@ -30,7 +30,7 @@
 
 #include "../generic/py_capi_utils.h"
 
-bContext*	__py_context = NULL;
+static bContext*	__py_context = NULL;
 bContext*	BPy_GetContext(void) { return __py_context; }
 void		BPy_SetContext(bContext *C) { __py_context= C; }