lib: Promote byte_conversions.h #include to hivex-internal.h

This patch addresses a build failure in OS X.  Running git-bisect on a
straightforward build (bootstrap, autogen.sh, configure, make, make
install) showed this as the "Bad commit:"
3e7c039

The issue is that hivex-internal.h uses le32toh in a static inline
function.  In case `configure` doesn't find le32toh, byte_conversions.h
defines it.  But hivex-internal.h doesn't include the safety definition.

OS X demonstrates this a problem.  Neither endian.h nor byteswap.h are
found with `configure` in OS X 10.8.5 (XCode 5), but the headers are
both found in Fedora 19 and Ubuntu 13.04.  This patch to configure.ac
further logs that only ntohl is available for byte swaps:

    @@ -153,6 +153,8 @@ AC_REPLACE_FUNCS([mmap])
     dnl Functions.
     AC_CHECK_FUNCS([bindtextdomain])

    +AC_CHECK_FUNCS([le32toh ntohl bswap_32 __bswap_32])
    +

(As an aside, it's curious that a missing byteswap.h didn't cause
hivex-internal.h to fail to build.)
(As another aside, this is an interesting example of lazy symbol
binding failing with an inline function.)

The problem is resolved by having hivex-internal.h include
byte_conversions.h.  This obviates most of the other direct inclusions
of byte_conversions.h.  (One persists under sh/.)

This patch builds and runs hivexml on images/large fine in Ubuntu 13.04
and Fedora 19.  It also allows builds to succeed in OS X, but doesn't
run hivexml for an unrelated reason.  The _iconv_open
symbol-not-found issue, that I thought was previously resolved
(491ba0f), resurfaced.

Signed-off-by: Alex Nelson <a.nelson@prometheuscomputing.com>

lib/handle.c

@@ -44,7 +44,6 @@
 
 #include "hivex.h"
 #include "hivex-internal.h"
-#include "byte_conversions.h"
 
 static uint32_t
 header_checksum (const hive_h *h)

lib/hivex-internal.h

@@ -22,6 +22,8 @@
 #include <stdarg.h>
 #include <stddef.h>
 
+#include "byte_conversions.h"
+
 struct hive_h {
   char *filename;
   int fd;

lib/node.c

@@ -34,7 +34,6 @@
 
 #include "hivex.h"
 #include "hivex-internal.h"
-#include "byte_conversions.h"
 
 hive_node_h
 hivex_root (hive_h *h)

lib/utf16.c

@@ -27,7 +27,6 @@
 
 #include "hivex.h"
 #include "hivex-internal.h"
-#include "byte_conversions.h"
 
 char *
 _hivex_windows_utf16_to_utf8 (/* const */ char *input, size_t len)

lib/value.c

@@ -32,7 +32,6 @@
 
 #include "hivex.h"
 #include "hivex-internal.h"
-#include "byte_conversions.h"
 
 int
 _hivex_get_values (hive_h *h, hive_node_h node,

lib/visit.c

@@ -32,7 +32,6 @@
 
 #include "hivex.h"
 #include "hivex-internal.h"
-#include "byte_conversions.h"
 
 int
 hivex_visit (hive_h *h, const struct hivex_visitor *visitor, size_t len,

lib/write.c

@@ -41,7 +41,6 @@
 
 #include "hivex.h"
 #include "hivex-internal.h"
-#include "byte_conversions.h"
 
 /*----------------------------------------------------------------------
  * Writing.