Channel names are case insensitive

But some servers (epiknet for example) send channel names with an uppercase

src/utils/tolower.hpp

@@ -0,0 +1,18 @@
+#ifndef TOLOWER_INCLUDED
+# define TOLOWER_INCLUDED
+
+#include <string>
+
+namespace utils
+{
+  std::string tolower(const std::string& original)
+  {
+    std::string res;
+    res.reserve(original.size());
+    for (const char c: original)
+      res += static_cast<char>(std::tolower(c));
+    return res;
+  }
+}
+
+#endif // SPLIT_INCLUDED