Upgrade Intel C++ compiler to icpc (ICC) 15.0.3 20150407

This resolves a whole range of issues and work-arounds with earlier
releases.  This version of icpc is more or less compatible with the
latest gcc and clang compilers and only required one hack to avoid
warnings from PackedBoolList.H.

wmake/rules/linuxIcc/c++

@@ -1,6 +1,7 @@
 SUFFIXES += .C
 
-c++WARN     = -wd327,525,654,819,1125,1476,1505,1572
+c++WARN     = -Wall -Wextra -Wnon-virtual-dtor -Wno-unused-parameter -Wno-invalid-offsetof \
+              -diag-disable 2304
 
 CC          = icpc -std=c++0x -fp-trap=common -fp-model precise