remove useles parentheses in macros - recent compilers don't like them (#98)

Avoid warnings as:
| ../../distrho/src/lv2/atom-util.h:334:2: note: in expansion of macro 'LV2_ATOM_OBJECT_FOREACH'
|   LV2_ATOM_OBJECT_FOREACH(object, prop) {
|   ^~~~~~~~~~~~~~~~~~~~~~~
| ../../distrho/src/lv2/atom-util.h: In function 'int lv2_atom_object_body_get(uint32_t, const LV2_Atom_Object_Body*, ...)':
| ../../distrho/src/lv2/atom-util.h:279:37: warning: unnecessary parentheses in declaration of 'prop' [-Wparentheses]
|   for (const LV2_Atom_Property_Body* (iter) = lv2_atom_object_begin(body); \
|                                      ^
| ../../distrho/src/lv2/atom-util.h:367:2: note: in expansion of macro 'LV2_ATOM_OBJECT_BODY_FOREACH'
|   LV2_ATOM_OBJECT_BODY_FOREACH(body, size, prop) {
|   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
| ../../distrho/src/lv2/atom-util.h: In function 'int lv2_atom_object_get(const LV2_Atom_Object*, ...)':
| ../../distrho/src/lv2/atom-util.h:273:37: warning: unnecessary parentheses in declaration of 'prop' [-Wparentheses]
|   for (const LV2_Atom_Property_Body* (iter) = lv2_atom_object_begin(&(obj)->body); \
                                     ^
Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>

distrho/src/lv2/atom-util.h

@@ -270,13 +270,13 @@ lv2_atom_object_next(const LV2_Atom_Property_Body* i)
    @endcode
 */
 #define LV2_ATOM_OBJECT_FOREACH(obj, iter) \
-	for (const LV2_Atom_Property_Body* (iter) = lv2_atom_object_begin(&(obj)->body); \
+	for (const LV2_Atom_Property_Body* iter = lv2_atom_object_begin(&(obj)->body); \
 	     !lv2_atom_object_is_end(&(obj)->body, (obj)->atom.size, (iter)); \
 	     (iter) = lv2_atom_object_next(iter))
 
 /** Like LV2_ATOM_OBJECT_FOREACH but for a headerless object body. */
 #define LV2_ATOM_OBJECT_BODY_FOREACH(body, size, iter) \
-	for (const LV2_Atom_Property_Body* (iter) = lv2_atom_object_begin(body); \
+	for (const LV2_Atom_Property_Body* iter = lv2_atom_object_begin(body); \
 	     !lv2_atom_object_is_end(body, size, (iter)); \
 	     (iter) = lv2_atom_object_next(iter))