campaignd: Use utf8::lowercase() instead of a direct call to libc tol…

…ower()

Note that the next loop in the same chunk of code already uses
utf8::lowercase() even though both strings are really of the same
nature.

src/campaign_server/campaign_server.cpp

@@ -521,9 +521,10 @@ namespace {
 
 						LOG_CS << "uploading campaign '" << upload["name"] << "' from " << addr << ".\n";
 						config &data = upload.child("data");
+
 						const std::string& name = upload["name"];
-						std::string lc_name(name.size(), ' ');
-						std::transform(name.begin(), name.end(), lc_name.begin(), tolower);
+						const std::string& lc_name = utf8::lowercase(name);
+
 						config *campaign = NULL;
 						BOOST_FOREACH(config &c, campaigns().child_range("campaign")) {
 							if (utf8::lowercase(c["name"]) == lc_name) {