Subzero: Improve class definition hygiene.

crosstest/vectors.h

 //===- subzero/crosstest/vectors.h - Common SIMD vector utilies -*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file provides declarations for PNaCl portable SIMD vector types. In
@@ skipping 82 matching lines @@
 }
 
 // In some crosstests, test vectors are deterministically constructed by
 // selecting elements from a pool of scalar values based on a
 // pseudorandom sequence.  Testing all possible combinations of scalar
 // values from the value pool is often not tractable.
 //
 // TODO: Replace with a portable PRNG from C++11.
 class PRNG {
 public:
-  PRNG(uint32_t Seed = 1) : State(Seed) {}
+  explicit PRNG(uint32_t Seed = 1) : State(Seed) {}
 
   uint32_t operator()() {
     // Lewis, Goodman, and Miller (1969)
     State = (16807 * State) % 2147483647;
     return State;
   }
 
 private:
   uint32_t State;
 };
 
 } // end anonymous namespace
 
 #endif // VECTORS_H