libCom: Use OS NAN and INFINITY macros where available.

bug: 545385

src/libCom/osi/epicsMath.cpp

@@ -1,5 +1,5 @@
 /*************************************************************************\
-* Copyright (c) 2009 UChicago Argonna LLC, as Operator of Argonne
+* Copyright (c) 2010 UChicago Argonna LLC, as Operator of Argonne
 *     National Laboratory.
 * EPICS BASE is distributed subject to a Software License Agreement found
 * in file LICENSE that is included with this distribution. 
@@ -14,21 +14,27 @@
 #pragma warning(disable:4723)
 #endif
 
+#ifndef NAN
 static float makeNAN ( void )
 {
     float a = 0, b = 0;
     return a / b;
 }
+#define NAN makeNAN()
+#endif
 
+#ifndef INFINITY
 static float makeINF ( void )
 {
     float a = 1, b = 0;
     return a / b;
 }
+#define INFINITY makeINF()
+#endif
 
 extern "C" {
-epicsShareDef float epicsNAN = makeNAN();
-epicsShareDef float epicsINF = makeINF();
+epicsShareDef float epicsNAN = NAN;
+epicsShareDef float epicsINF = INFINITY;
 }
 
 #ifdef _MSC_VER