Resolve unnecessary_transmutes warning in nightly-2025-04-25

[dtolnay]

rust-lang/rust#136083

warning: unnecessary transmute
   --> src/diyfp.rs:141:37
    |
141 |                   let u: $mask_type = mem::transmute(d);
    |                                       ^^^^^^^^^^^^^^^^^ help: replace this with: `f32::to_bits(d)`
    |
   ::: src/lib.rs:197:9
    |
197 | /         dtoa! {
198 | |             floating_type: f32,
199 | |             significand_type: u32,
200 | |             exponent_type: i32,
...   |
211 | |             min_power: (-36),
212 | |         };
    | |_________- in this macro invocation
    |
    = note: `#[warn(unnecessary_transmutes)]` on by default
    = note: this warning originates in the macro `diyfp` which comes from the expansion of the macro `dtoa` (in Nightly builds, run with -Z macro-backtrace for more info)

warning: unnecessary transmute
   --> src/diyfp.rs:141:37
    |
141 |                   let u: $mask_type = mem::transmute(d);
    |                                       ^^^^^^^^^^^^^^^^^ help: replace this with: `f64::to_bits(d)`
    |
   ::: src/lib.rs:243:9
    |
243 | /         dtoa! {
244 | |             floating_type: f64,
245 | |             significand_type: u64,
246 | |             exponent_type: isize,
...   |
257 | |             min_power: (-348),
258 | |         };
    | |_________- in this macro invocation
    |
    = note: this warning originates in the macro `diyfp` which comes from the expansion of the macro `dtoa` (in Nightly builds, run with -Z macro-backtrace for more info)