Fix out-of-bounds read in hex_decode

The range check is off by 1.
The input letter 'p' makes an out-of-bounds read.
The resulting byte is unpredictable.

Affects the <bytes> argument of the command "vm_debug pmem_cfind".

Since: 7ba3d15

common/utils.c

@@ -200,7 +200,7 @@ int hex_decode(unsigned char *out,const unsigned char *in,int maxlen)
    int empty = TRUE;
 
    for(;len < maxlen;) {
-      if (*in > sizeof(hexval) || hexval[*in] == BAD)
+      if (*in >= sizeof(hexval) || hexval[*in] == BAD)
          break;
 
       if (empty) {