Handle libtiff the same way as libpng and libjpeg

libtiff is the odd one out where support was detected in two places
and it was handled a different way than the other two.

acinclude.m4

@@ -313,6 +313,9 @@ AC_DEFUN([SANE_CHECK_TIFF],
     AC_CHECK_HEADER(tiffio.h,
     [sane_cv_use_libtiff="yes"; TIFF_LIBS="-ltiff"],)
   ],)
+  if test "$sane_cv_use_libtiff" = "yes" ; then
+     AC_DEFINE(HAVE_LIBTIFF,1,[Define to 1 if you have the libtiff library.])
+  fi
   AC_SUBST(TIFF_LIBS)
 ])
 

backend/escl/escl_capabilities.c

@@ -232,7 +232,7 @@ find_valor_of_array_variables(xmlNode *node, capabilities_t *scanner, int type)
 	       scanner->caps[type].have_png = i;
             }
 #endif
-#if(defined HAVE_TIFFIO_H)
+#if(defined HAVE_LIBTIFF)
             else if(!strcmp(scanner->caps[type].DocumentFormats[i], "image/tiff"))
             {
                have_tiff = SANE_TRUE;

backend/escl/escl_tiff.c

@@ -35,14 +35,14 @@
 #include <string.h>
 #include <unistd.h>
 
-#if(defined HAVE_TIFFIO_H)
+#if(defined HAVE_LIBTIFF)
 #include <tiffio.h>
 #endif
 
 #include <setjmp.h>
 
 
-#if(defined HAVE_TIFFIO_H)
+#if(defined HAVE_LIBTIFF)
 
 /**
  * \fn SANE_Status escl_sane_decompressor(escl_sane_t *handler)

backend/genesys/image.cpp

@@ -22,7 +22,7 @@
 
 #include "image.h"
 
-#if defined(HAVE_TIFFIO_H)
+#if defined(HAVE_LIBTIFF)
 #include <tiffio.h>
 #endif
 
@@ -187,7 +187,7 @@ void write_tiff_file(const std::string& filename, const void* data, int depth, i
 {
     DBG_HELPER_ARGS(dbg, "depth=%d, channels=%d, ppl=%d, lines=%d", depth, channels,
                     pixels_per_line, lines);
-#if defined(HAVE_TIFFIO_H)
+#if defined(HAVE_LIBTIFF)
     auto image = TIFFOpen(filename.c_str(), "w");
     if (!image) {
         dbg.log(DBG_error, "Could not save debug image");

backend/hp3900_debug.c

@@ -47,7 +47,7 @@
 #define DBG_BLK             0x04	/* USB Bulk data                 */
 
 #include <stdarg.h>
-#ifdef HAVE_TIFFIO_H
+#ifdef HAVE_LIBTIFF
 #include <tiffio.h>		/* dbg_tiff_save */
 #endif
 
@@ -545,7 +545,7 @@ dbg_tiff_save (char *sFile, SANE_Int width, SANE_Int height, SANE_Int depth,
 	       SANE_Int colortype, SANE_Int res_x, SANE_Int res_y,
 	       SANE_Byte * buffer, SANE_Int size)
 {
-#ifdef HAVE_TIFFIO_H
+#ifdef HAVE_LIBTIFF
   if (buffer != NULL)
     {
       char *path = getenv ("HOME");

configure.ac

@@ -201,7 +201,7 @@ AC_CHECK_HEADERS(fcntl.h unistd.h libc.h sys/dsreq.h sys/select.h \
     sys/socket.h sys/io.h sys/hw.h sys/types.h linux/ppdev.h \
     dev/ppbus/ppi.h machine/cpufunc.h sys/sem.h poll.h \
     windows.h be/kernel/OS.h limits.h sys/ioctl.h asm/types.h\
-    netinet/in.h tiffio.h ifaddrs.h pwd.h getopt.h)
+    netinet/in.h ifaddrs.h pwd.h getopt.h)
 AC_CHECK_HEADERS([asm/io.h],,,[#include <sys/types.h>])
 
 SANE_CHECK_MISSING_HEADERS