add missing #include<cmath> to make some compilers happy.

src/classes/PRgeHandler.cpp

@@ -32,6 +32,7 @@
 #include <vector>
 #include <string>
 #include <memory>
+#include <cmath>
 
 #include <boost/filesystem.hpp>
 #include <boost/algorithm/string.hpp>

src/external/Nonlocal/prog/dump_nonlocal_field.cpp

@@ -33,6 +33,7 @@
 #include <vector>
 #include <map>
 #include <cstring>
+#include <cmath>
 
 #include <boost/algorithm/string.hpp>
 

src/musredit_qt6/mupp/plotter/PMuppCanvas.cpp

@@ -53,6 +53,7 @@
 #include <cstdlib>
 #include <iostream>
 #include <fstream>
+#include <cmath>
 
 #include <TColor.h>
 #include <TROOT.h>