Fix hash table issues with ISO C99

ISO C99 forbids unnamed structs/unions and nested functions. Move the
"HTABLE_HEAD" and "HTABLE_GENERATE" parts out of the function body and
place them at the very top of the file (where function definitions are
allowed). Also, remove the unnamed struct from "htable.h" (which was
useless anyway).

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/htable.h

@@ -69,9 +69,7 @@ struct name {                                                                 \
 }
 
 #define HTABLE_ENTRY(type)                                                    \
-struct {                                                                      \
-  struct type   *next;         /* To build the bucket chain list. */          \
-}
+struct type   *next          /* To build the bucket chain list. */
 
 #define HTABLE_SIZE(head)                                                     \
   (sizeof (*(head)->bkts) ? sizeof ((head)->bkts) / sizeof (*(head)->bkts) : 0)