[Bug middle-end/62103] Incorrect folding of bitfield in a union on big endian targets

[thopre01 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62103

--- Comment #11 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Ok, I have a local fix. The existing testcase didn't catch it because the
precision of the bitfield is not a multiple of CHAR_BITS.