Include the correct header for std::lower_bound.

That is <algorithm>. Relying on indirect includes is bad, mmkay?

Change-Id: I245885672004cd406f98c82231aaa38a5cfe464c
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/plugins/cpptools/includeutils.cpp

@@ -42,6 +42,8 @@
 #include <QTextBlock>
 #include <QTextDocument>
 
+#include <algorithm>
+
 using namespace CPlusPlus;
 using namespace CppTools;
 using namespace CppTools::IncludeUtils;