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/modifiers/intern/MOD_shapekey.c

@@ -128,20 +128,20 @@ ModifierTypeInfo modifierType_ShapeKey = {
 	/* flags */             eModifierTypeFlag_AcceptsCVs
 							| eModifierTypeFlag_SupportsEditmode,
 
-	/* copyData */          0,
+	/* copyData */          NULL,
 	/* deformVerts */       deformVerts,
 	/* deformMatrices */    deformMatrices,
 	/* deformVertsEM */     deformVertsEM,
 	/* deformMatricesEM */  deformMatricesEM,
-	/* applyModifier */     0,
-	/* applyModifierEM */   0,
-	/* initData */          0,
-	/* requiredDataMask */  0,
-	/* freeData */          0,
-	/* isDisabled */        0,
-	/* updateDepgraph */    0,
-	/* dependsOnTime */     0,
-	/* dependsOnNormals */	0,
-	/* foreachObjectLink */ 0,
-	/* foreachIDLink */     0,
+	/* applyModifier */     NULL,
+	/* applyModifierEM */   NULL,
+	/* initData */          NULL,
+	/* requiredDataMask */  NULL,
+	/* freeData */          NULL,
+	/* isDisabled */        NULL,
+	/* updateDepgraph */    NULL,
+	/* dependsOnTime */     NULL,
+	/* dependsOnNormals */	NULL,
+	/* foreachObjectLink */ NULL,
+	/* foreachIDLink */     NULL
 };