Fix handling of non-integral bit-fields in native_encode_initializer
The encoder for CONSTRUCTORs assumes that all bit-fields (DECL_BIT_FIELD)
have integral types, but that's not the case in Ada where they may have
pretty much any type, resulting in a wrong encoding for them
gcc/
* fold-const.cc (native_encode_initializer) <CONSTRUCTOR>: Apply the
specific treatment for bit-fields only if they have an integral type
and filter out non-integral bit-fields that do not start and end on
a byte boundary.
gcc/testsuite/
* gnat.dg/opt101.adb: New test.
* gnat.dg/opt101_pkg.ads: New helper.