1 << BITS_PER_UNIT

[Michael Hayes]

While there's a crusade on to remove egcs compilation warnings, here's
one for interested folks to consider.

It regards the use of (1 << BITS_PER_UNIT), usually when computing a
bit mask with (1 << BITS_PER_UNIT) - 1, when BITS_PER_UNIT is equal to
the number of bits in a HOST_LONG_INT.  This occurs with the C4x
target where BITS_PER_UNIT is 32.  Maybe there should be a macro,
say BITS_PER_UNIT_MASK?

Michael.