relax is_a heic test rules

32 was a little too small, see https://github.com/libvips/libvips/issues/1861

ChangeLog

@@ -1,3 +1,6 @@
+18/10/20 started 8.10.3
+- relax heic is_a rules [hisham]
+
 6/9/20 started 8.10.2
 - update magicksave/load profile handling [kelilevi]
 - better demand hint rules [kaas3000]

configure.ac

@@ -2,7 +2,7 @@
 
 # also update the version number in the m4 macros below
 
-AC_INIT([vips], [8.10.2], [vipsip@jiscmail.ac.uk])
+AC_INIT([vips], [8.10.3], [vipsip@jiscmail.ac.uk])
 # required for gobject-introspection
 AC_PREREQ(2.62)
 
@@ -18,7 +18,7 @@ AC_CONFIG_MACRO_DIR([m4])
 # user-visible library versioning
 m4_define([vips_major_version], [8])
 m4_define([vips_minor_version], [10])
-m4_define([vips_micro_version], [2])
+m4_define([vips_micro_version], [3])
 m4_define([vips_version],
           [vips_major_version.vips_minor_version.vips_micro_version])
 
@@ -38,7 +38,7 @@ VIPS_VERSION_STRING=$VIPS_VERSION-`date -u -r $srcdir/ChangeLog`
 #   binary interface changes not backwards compatible?: reset age to 0
 
 LIBRARY_CURRENT=54
-LIBRARY_REVISION=4
+LIBRARY_REVISION=5
 LIBRARY_AGE=12
 
 # patched into include/vips/version.h

libvips/foreign/heifload.c

@@ -271,7 +271,7 @@ static const char *heif_magic[] = {
  *
  *	enum heif_filetype_result result = heif_check_filetype( buf, 12 );
  *
- * but it's very conservative and seems to be missing some of the Nokia hief
+ * but it's very conservative and seems to be missing some of the Nokia heif
  * types.
  */
 static int
@@ -282,7 +282,10 @@ vips_foreign_load_heif_is_a( const char *buf, int len )
 
 		int i;
 
-		if( chunk_len > 32 || 
+                /* We've seen real files with 36 here, so 64 should be
+                 * plenty.
+                 */
+		if( chunk_len > 64 || 
 			chunk_len % 4 != 0 )
 			return( 0 );