(HARD_REG_ELT_TYPE): New unsigned type to
avoid signed arithmetic overflow.
(HARD_REG_SET): Define as HARD_REG_ELT_TYPE, or array thereof.
(HARD_CONST): Always cast to HARD_REG_ELT_TYPE.
(*_HARD_REG_*): Use unsigned HARD_CONST and HARD_REG_ELT_TYPE
types instead of assuming HOST_WIDE_INT.

From-SVN: r4901