Specify namespace of math functions to avoid name clashes

In the 4.6.x range of GNU compilers, the cmath header include math.h, adding
isinf() and isnan() to the global namespace as well as std. When used in if
statements, there is then an ambiguity between the std version which returns
bool and the global function which returns int; for more details see:
<http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48891>

If we qualify the functions explicitly with their namespace, this error goes
away.

examples/upscale_cap.cpp

@@ -553,7 +553,7 @@ int main(int varnum, char** vararg)
        }
        
        // Check for saneness of Ptestvalue:
-       if (isnan(Ptestvalue) | isinf(Ptestvalue)) {
+       if (std::isnan(Ptestvalue) || std::isinf(Ptestvalue)) {
            cerr << "ERROR: Ptestvalue was inf or nan" << endl;
            break; // Jump out of while-loop, just print out the results
            // up to now and exit the program

examples/upscale_cond.cpp

@@ -713,7 +713,7 @@ int main(int varnum, char** vararg)
        }
        
        // Check for saneness of Ptestvalue:
-       if (isnan(Ptestvalue) | isinf(Ptestvalue)) {
+       if (std::isnan(Ptestvalue) || std::isinf(Ptestvalue)) {
            if (isMaster) cerr << "ERROR: Ptestvalue was inf or nan" << endl;
            break; // Jump out of while-loop, just print out the results
            // up to now and exit the program

examples/upscale_relperm.cpp

@@ -1187,7 +1187,7 @@ int main(int varnum, char** vararg)
        }
        
        // Check for saneness of Ptestvalue:
-       if (isnan(Ptestvalue) | isinf(Ptestvalue)) {
+       if (std::isnan(Ptestvalue) || std::isinf(Ptestvalue)) {
            if (isMaster) cerr << "ERROR: Ptestvalue was inf or nan" << endl;
            break; // Jump out of while-loop, just print out the results
            // up to now and exit the program

examples/upscale_relpermvisc.cpp

@@ -1081,7 +1081,7 @@ int main(int varnum, char** vararg)
         }
             
         // Check for saneness of fracFlowRatioTestvalue
-        if (isnan(fracFlowRatioTestvalue) || isinf(fracFlowRatioTestvalue)) {
+        if (std::isnan(fracFlowRatioTestvalue) || std::isinf(fracFlowRatioTestvalue)) {
             if (isMaster) cerr << "ERROR: fracFlowRatioTestvalue was inf or nan." << endl;
             break; // Jump out out while-loop, just print the results up to now and exit
         }