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/blenlib/intern/BLI_args.c

@@ -39,7 +39,7 @@
 #include "BLI_args.h"
 #include "BLI_ghash.h"
 
-char NO_DOCS[] = "NO DOCUMENTATION SPECIFIED";
+static char NO_DOCS[] = "NO DOCUMENTATION SPECIFIED";
 
 struct bArgDoc;
 typedef struct bArgDoc {