upgrade vendored libtiff to 4.6.0

Closes: #397

.gitmodules

@@ -17,7 +17,7 @@
 [submodule "external/libtiff"]
 	path = external/libtiff
 	url = https://github.com/libsdl-org/libtiff.git
-	branch = v4.5.1-SDL
+	branch = v4.6.0-SDL
 [submodule "external/zlib"]
 	path = external/zlib
 	url = https://github.com/libsdl-org/zlib.git

VisualC/external/include/tiff.h

@@ -646,7 +646,7 @@ typedef enum
 #define TIFFTAG_EP_EXPOSUREINDEX 37397            /* Exposure index */
 #define TIFFTAG_EP_STANDARDID 37398               /* TIFF/EP standard version, n.n.n.n */
 #define TIFFTAG_EP_SENSINGMETHOD 37399            /* Type of image sensor */
-/* 
+/*
  * TIFF/EP tags equivalent to EXIF tags
  *     Note that TIFF-EP and EXIF use nearly the same metadata tag set, but TIFF-EP stores the tags in IFD 0,
  *     while EXIF store the tags in a separate IFD. Either location is allowed by DNG, but the EXIF location is preferred.
@@ -761,6 +761,7 @@ typedef enum
 #define TIFFTAG_LERC_MAXZERROR 65567   /* LERC maximum error */
 #define TIFFTAG_WEBP_LEVEL 65568       /* WebP compression level */
 #define TIFFTAG_WEBP_LOSSLESS 65569    /* WebP lossless/lossy */
+#define TIFFTAG_WEBP_LOSSLESS_EXACT 65571  /* WebP lossless exact mode. Set-only mode. Default is 1. Can be set to 0 to increase compression rate, but R,G,B in areas where alpha = 0 will not be preserved */
 #define TIFFTAG_DEFLATE_SUBCODEC 65570 /* ZIP codec: to get/set the sub-codec to use. Will default to libdeflate when available */
 #define DEFLATE_SUBCODEC_ZLIB 0
 #define DEFLATE_SUBCODEC_LIBDEFLATE 1

VisualC/external/include/tiffio.h

@@ -277,7 +277,7 @@ typedef struct
 #define LOGLUV_PUBLIC 1
 #endif
 
-#if defined(__GNUC__) || defined(__attribute__)
+#if defined(__GNUC__) || defined(__clang__) || defined(__attribute__)
 #define TIFF_ATTRIBUTE(x) __attribute__(x)
 #else
 #define TIFF_ATTRIBUTE(x) /*nothing*/

VisualC/external/include/tiffvers.h

@@ -1,22 +1,28 @@
+/* tiffvers.h version information is updated according to version information
+ * in configure.ac */
+
 /* clang-format off */
 
 /* clang-format disabled because FindTIFF.cmake is very sensitive to the
  * formatting of below line being a single line.
+ * Furthermore, configure_file variables of type "@VAR@" are
+ * modified by clang-format and won't be substituted by CMake.
  */
-#define TIFFLIB_VERSION_STR "LIBTIFF, Version 4.5.1\nCopyright (c) 1988-1996 Sam Leffler\nCopyright (c) 1991-1996 Silicon Graphics, Inc."
+#define TIFFLIB_VERSION_STR "LIBTIFF, Version 4.6.0\nCopyright (c) 1988-1996 Sam Leffler\nCopyright (c) 1991-1996 Silicon Graphics, Inc."
 /*
  * This define can be used in code that requires
  * compilation-related definitions specific to a
  * version or versions of the library.  Runtime
  * version checking should be done based on the
  * string returned by TIFFGetVersion.
  */
-#define TIFFLIB_VERSION 20230609
+#define TIFFLIB_VERSION 20230908
 
 /* The following defines have been added in 4.5.0 */
 #define TIFFLIB_MAJOR_VERSION 4
-#define TIFFLIB_MINOR_VERSION 5
-#define TIFFLIB_MICRO_VERSION 1
+#define TIFFLIB_MINOR_VERSION 6
+#define TIFFLIB_MICRO_VERSION 0
+#define TIFFLIB_VERSION_STR_MAJ_MIN_MIC "4.6.0"
 
 /* Macro added in 4.5.0. Returns TRUE if the current libtiff version is
  * greater or equal to major.minor.micro