Since there are more platforms that do not have symbols present, we need
to use `rustc_apfloat` for more conversion tests. Make use of the
fallback like other tests, and refactor so each test gets its own
function.
Previously we were testing both apfloat and system conversion methods
when possible. This changes to only test one or the other, depending on
whether or not the system version is available. This seems reasonable
because it is consistent with all other tests, but we should consider
updating all tests to check both at some point.
This also includes an adjustment of PowerPC configuration to account for
the linking errors at [1].
[1]: https://github.com/rust-lang/compiler-builtins/issues/655
PowerPC platforms use `kf` rather than `tf` for `f128`. Add a way to
alias this in the macro to make the code cleaner.
This also fixes the names of `fixunstf*` and `fixtf*` on Power PC
(`fixunskf*` and `fixkf*` are correct).
Currently, tests of the same kind are grouped together across all types
into a single function. This makes it difficult to understand exactly
what failed in CI.
Change test macros to create separate functions for separate types so
failures are more fine grained.
