top: fix selected miscellaneous compiler warnings

top: fix selected miscellaneous compiler warnings

   These per instance warnings have been eliminated:
warning: range expressions in switch statements are non-standard
warning: padding struct to align 'winflags'
warning: dereferencing type-punned pointer will break strict-aliasing rules

   These per instance warnings have not been addressed
   since they simply trade one warning for another:
      From:
warning: ISO C does not permit named variadic macros
warning: ISO C does not support the '%Lu' gnu_scanf format
      To:
warning: anonymous variadic macros were introduced in C99
warning: ISO C90 does not support the 'll' gnu_scanf length modifier

   Lastly, since all C compilers have supported use of
   C++ style comments for the past 20 years, the top
   program will never trade them for the often more
   cumbersome C style comments simply to avoid this
   once per source file warning:
warning: C++ style comments are not allowed in ISO C90

Signed-off-by: Jim Warner <james.warner@comcast.net>