libCom: add EPICS_FUNCTION

Automatic macro which expands to the current function name.
Useful in debug prints.

src/libCom/test/epicsAtomicTest.cpp

@@ -406,6 +406,7 @@ MAIN ( epicsAtomicTest )
 {
 
     testPlan ( 50 );
+    testDiag("In %s", EPICS_FUNCTION);
     testClassify ();
     testBasic();
 #if defined(__rtems__)