More cleanup

Author: brt-v

include/pcg/pcg_random.hpp

@@ -279,11 +279,11 @@ class specific_stream {
     using state_type   = itype;
     using stream_state = itype;
 
-    constexpr itype increment() const {
+    [[nodiscard]] constexpr itype increment() const {
         return inc_;
     }
 
-    constexpr  itype stream() const
+    [[nodiscard]] constexpr itype stream() const
     {
          return inc_ >> 1;
     }
@@ -815,9 +815,9 @@ struct xsh_rr_mixin {
         constexpr bitcount_t topspare    = opbits;
         constexpr bitcount_t bottomspare = sparebits - topspare;
         constexpr bitcount_t xshift      = (topspare + xtypebits)/2;
-        bitcount_t rot = opbits ? bitcount_t(internal >> (bits - opbits)) & mask
+        const  rot = opbits ? bitcount_t(internal >> (bits - opbits)) & mask
                                 : 0;
-        bitcount_t amprot = (rot << amplifier) & mask;
+        const bitcount_t amprot = (rot << amplifier) & mask;
         internal ^= internal >> xshift;
         xtype result = xtype(internal >> bottomspare);
         result = rotr(result, amprot);
@@ -1143,8 +1143,8 @@ template <typename baseclass>
 struct inside_out : private baseclass {
     inside_out() = delete;
 
-    typedef typename baseclass::result_type result_type;
-    typedef typename baseclass::state_type  state_type;
+    using result_type = baseclass::result_type;
+    using state_type = baseclass::state_type;
     static_assert(sizeof(result_type) == sizeof(state_type),
                   "Require a RNG whose output function is a permutation");