Disable following warnings when cross-compiling with a gcc older
  than 3.0, to avoid warnings from third party system headers:

    -Wmissing-prototypes
    -Wunused
    -Wshadow

  Do not enable -pedantic when cross-compiling with a gcc older
  than 3.0, to avoid warnings from third party system headers.

  Highest warning level is double -A, next is single -A.
  Due to the big number of warnings these trigger on third
  party header files it is impratical for us to use any of
  them here. If you want them simply define it in CPPFLAGS.

  Warning level reduced from double -A to single -A

2) Disable SGI remark: controlling expression is constant

  Due to the HP-UX socklen_t issue it is insane to use the +w1 warning level.
  It generates more than 1100 warnings on socklen_t related statements.

  Until the issue is somehow fixed we will just use the +w2 warning level.

  Disallow run-time dereferencing of null pointers.

  Disable some remarks:

    #4227: padding struct with n bytes to align member.

    #4255: padding size of struct with n bytes to alignment boundary.

option to specify dis(activation) of compiler optimizations.

If option is specified, it will be honored independant of the
--(dis|en)able-debug option.

option to specify dis(activation) of picky compiler warnings.

If option is specified, it will be honored independant of the
--(dis|en)able-debug option.

If option is not specified, it will follow --(dis|en)able-debug
setting, whose default is disabled if not specified.