(FLO_union_type): Remove bitfields to set sign, exponent, and

(FLO_union_type): Remove bitfields to set sign, exponent, and
mantissa, and add value_raw field, which is an integer of the
appropriate type.  If _DEBUG_BITFLOAT is defined, provide little and
big endian bitfields.  If the macro FLOAT_BIT_ORDER_MISMATCH is
defined, use explicit bitfields.
(pack_d, unpack_d): Switch to use value_raw and explicit shifts and
masks so that we don't have to worry about whether the target is big
or little endian unless FLOAT_BIT_ORDER_MISMATCH is defined.  If
single precision floating point, rename to pack_f and unpack_f, so
there is no confusion in the debugger.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@10313 138bc75d-0d04-0410-961f-82ee72b054a4