fp-bit.h: Define macros for TFmode floating-point constants in IBM-extended TFmode types.

* fp-bit.h: Define macros for TFmode floating-point constants
in IBM-extended TFmode types.
(TMODES): Define if __LDBL_MANT_DIG__ has the newly-supported
widths.
* config/fp-bit.c (pack_d, unpack_d): Support IBM-extended
TFmode type.

From-SVN: r61837