cleanup: replace membuffer by membufferpp in C-code

Thus, the membuffer data is automatically freed when going
out of scope - one thing less to worry about.

This fixes one use-after-free bug in uploadDiveLogsDE.cpp
and one extremely questionable practice in divetooltipitem.cpp:
The membuffer was a shared instance across all instances
of the DiveToolTipItem.

Remves unnecessary #include directives in files that didn't
even use membuffer.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/uploadDiveShare.cpp

@@ -27,10 +27,9 @@ uploadDiveShare::uploadDiveShare():
 void uploadDiveShare::doUpload(bool selected, const QString &uid, bool noPublic)
 {
 	//generate json
-	struct membuffer buf = {};
+	struct membufferpp buf;
 	export_list(&buf, NULL, selected, false);
 	QByteArray json_data(buf.buffer, buf.len);
-	free_buffer(&buf);
 
 	//Request to server
 	QNetworkRequest request;