Add test coverage for infinite inputs

Author: mtilda

src/float.rs

@@ -2434,7 +2434,7 @@ mod tests {
                 let deviation = recovered_input - input;
 
                 assert!(
-                    deviation.abs() < $tolerance,
+                    recovered_input == input || deviation.abs() < $tolerance,
                     "failed to recover input of `Float::integer_decode({0:e})`
 \t expected: ~ {:e}
 \t    found:   {:e}
@@ -2469,6 +2469,7 @@ mod tests {
             check(sign_f * 5____f32, 0xa00000, -21, sign);
             check(sign_f * 42___f32, 0xa80000, -18, sign);
             check(sign_f * f32::MAX, 0xffffff, 104, sign);
+            check(sign_f * f32::INFINITY, 0x800000, 105, sign);
         }
     }
 
@@ -2492,6 +2493,7 @@ mod tests {
             check(sign_f * 5____f64, 0x14000000000000, -50, sign);
             check(sign_f * 42___f64, 0x15000000000000, -47, sign);
             check(sign_f * f64::MAX, 0x1fffffffffffff, 971, sign);
+            check(sign_f * f64::INFINITY, 0x10000000000000, 972, sign);
         }
     }