These configuration variables have been removed:
  GLIBMM_HAVE_C_STD_TIME_T_IS_NOT_INT32
  GLIBMM_MEMBER_FUNCTIONS_MEMBER_TEMPLATES
  GLIBMM_CAN_USE_NAMESPACES_INSIDE_EXTERNC
  GLIBMM_CAN_USE_THREAD_LOCAL
  GLIBMM_HAVE_NAMESPACE_STD
  GLIBMM_COMPILER_SUN_FORTE
  GLIBMM_EXCEPTIONS_ENABLED
  GLIBMM_PROPERTIES_ENABLED
  GLIBMM_VFUNCS_ENABLED
  GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
and this preprocessor macro:
  GLIBMM_USING_STD(Symbol)

The corresponding M4 macros in build/ and their calls in configure.ac have
also been removed.

Fixes #22