Giant const patch of doom: add a 'const' to every parameter in every

puzzle backend function which ought to have it, and propagate those
consts through to per-puzzle subroutines as needed.

I've recently had to do that to a few specific parameters which were
being misused by particular puzzles (r9657, r9830), which suggests
that it's probably a good idea to do the whole lot pre-emptively
before the next such problem shows up.

[originally from svn r9832]
[r9657 == 3b250baa02a7332510685948bf17576c397b8ceb]
[r9830 == 0b93de904a98f119b1a95d3a53029f1ed4bfb9b3]

random.c

@@ -107,7 +107,7 @@ void SHA_Init(SHA_State * s)
     s->lenhi = s->lenlo = 0;
 }
 
-void SHA_Bytes(SHA_State * s, void *p, int len)
+void SHA_Bytes(SHA_State * s, const void *p, int len)
 {
     unsigned char *q = (unsigned char *) p;
     uint32 wordblock[16];
@@ -188,7 +188,7 @@ void SHA_Final(SHA_State * s, unsigned char *output)
     }
 }
 
-void SHA_Simple(void *p, int len, unsigned char *output)
+void SHA_Simple(const void *p, int len, unsigned char *output)
 {
     SHA_State s;
 
@@ -207,7 +207,7 @@ struct random_state {
     int pos;
 };
 
-random_state *random_new(char *seed, int len)
+random_state *random_new(const char *seed, int len)
 {
     random_state *state;
 
@@ -304,7 +304,7 @@ char *random_state_encode(random_state *state)
     return dupstr(retbuf);
 }
 
-random_state *random_state_decode(char *input)
+random_state *random_state_decode(const char *input)
 {
     random_state *state;
     int pos, byte, digits;