enca: fix discard-qualifier warning in enca_eol_surface() (#99)

memchr() returns void* from a const unsigned char* buffer but was
assigned to a non-const unsigned char* p, discarding the const
qualifier. Change p to const unsigned char* to correctly propagate
constness from the buffer parameter.

Author: heitbaum

lib/guess.c

@@ -668,7 +668,7 @@ enca_eol_surface(const unsigned char *buffer,
                  size_t size,
                  const size_t *counts)
 {
-  unsigned char *p;
+  const unsigned char *p;
   size_t i;
 
   /* Return BINARY when the sample contains some strange characters.