* rtl.c: Define CONST_DOUBLE_FORMAT to the appropriate format
for a CONST_DOUBLE, at compile time. Initialize rtx_length
and class_narrowest_mode at compile time. Kill init_rtl.
Mark rtx_length, mode_class, mode_size, mode_unit_size,
mode_wider_mode, mode_mask_array, class_narrowest_mode, and
rtx_format as const. Kill all references to EXTRA_CC_MODES or
EXTRA_CC_NAMES.
* rtl.def (CONST_DOUBLE): Use CONST_DOUBLE_FORMAT macro for
format.
* rtl.h: Declare rtx_length and rtx_format as const.
* machmode.def: Define CC(). Use CC() to define CCmode. If
EXTRA_CC_MODES is defined, expand it here.
* machmode.h: Declare mode_class, mode_size, mode_unit_size,
mode_wider_mode, mode_mask_array, and class_narrowest_mode as
const. Kill all references to EXTRA_CC_MODES.