COMP: adjustments for nvc++ compiler

- remove unneeded -Wno-old-style flags with boost/cgal elements
- add nvc equivalent to gcc/clang -Wno-invalid-offsetof
- avoid warnings about set-but-unused variable and change of scoping

STYLE: remove wmake 'CGAL' rule
- was a transitional forward to 'cgal' rule since DEC-2020

applications/utilities/surface/surfaceBooleanFeatures/PolyhedronReader/Make/options

@@ -1,8 +1,6 @@
 EXE_NDEBUG = -DNDEBUG
 /* EXE_NDEBUG = -g -O0 -DFULLDEBUG */
 
-c++CGALWARN = -Wno-old-style-cast
-
 /*-- Define CGAL_INEXACT to use inexact CGAL constructions */
 
 include $(GENERAL_RULES)/cgal
@@ -11,7 +9,6 @@ EXE_INC = \
     ${ROUNDING_MATH} \
     ${EXE_NDEBUG} \
     ${CGAL_INC} \
-    ${c++LESSWARN} \
     -I.. \
     -I$(LIB_SRC)/surfMesh/lnInclude \
     -I$(LIB_SRC)/meshTools/lnInclude