Avoid use of from_bits until it is available in lib core

Also don't use --tests flag with 1.22 compiler.

Author: dhardy

.travis.yml

@@ -11,7 +11,8 @@ matrix:
     - rust: 1.22.0
       install:
       script:
-        - cargo test --tests --no-default-features
+        # TODO: use --tests instead of --lib on more recent compiler
+        - cargo test --lib --no-default-features
         - cargo test --package rand_core --no-default-features
         - cargo test --features serde1,log
     - rust: stable

src/distributions/float.rs

@@ -95,7 +95,9 @@ macro_rules! float_impls {
                 // The exponent is encoded using an offset-binary representation
                 let exponent_bits: $u_scalar =
                     (($exponent_bias + exponent) as $u_scalar) << $fraction_bits;
-                $ty::from_bits(self | exponent_bits)
+                // TODO: use from_bits when min compiler > 1.25 (see #545)
+                // $ty::from_bits(self | exponent_bits)
+                unsafe{ mem::transmute(self | exponent_bits) }
             }
         }