Revert "Use LV2_ATOM_BODY macros in examples instead of pointer arithmetic"

This reverts commit 3aad5eb1b0, which broke the
example plugins.

plugins/eg-fifths.lv2/fifths.c

@@ -128,7 +128,7 @@ run(LV2_Handle instance,
 	// Read incoming events
 	LV2_ATOM_SEQUENCE_FOREACH(self->in_port, ev) {
 		if (ev->body.type == uris->midi_Event) {
-			const uint8_t* const msg = (const uint8_t*)LV2_ATOM_BODY_CONST(ev);
+			const uint8_t* const msg = (const uint8_t*)(ev + 1);
 			switch (lv2_midi_message_type(msg)) {
 			case LV2_MIDI_MSG_NOTE_ON:
 			case LV2_MIDI_MSG_NOTE_OFF:

plugins/eg-midigate.lv2/midigate.c

@@ -161,7 +161,7 @@ run(LV2_Handle instance, uint32_t sample_count)
 
 	LV2_ATOM_SEQUENCE_FOREACH(self->control, ev) {
 		if (ev->body.type == self->uris.midi_MidiEvent) {
-			const uint8_t* const msg = (const uint8_t*)LV2_ATOM_BODY_CONST(ev);
+			const uint8_t* const msg = (const uint8_t*)(ev + 1);
 			switch (lv2_midi_message_type(msg)) {
 			case LV2_MIDI_MSG_NOTE_ON:
 				++self->n_active_notes;

plugins/eg-sampler.lv2/sampler.c

@@ -322,7 +322,7 @@ handle_event(Sampler* self, LV2_Atom_Event* ev)
 	PeaksURIs*   peaks_uris = &self->psend.uris;
 
 	if (ev->body.type == uris->midi_Event) {
-		const uint8_t* const msg = (const uint8_t*)LV2_ATOM_BODY_CONST(ev);
+		const uint8_t* const msg = (const uint8_t*)(ev + 1);
 		switch (lv2_midi_message_type(msg)) {
 		case LV2_MIDI_MSG_NOTE_ON:
 			self->frame = 0;