add vips_vipsload() vips_vipssave() to C API

we didn't have these in the C API before, for some reason

ChangeLog

@@ -17,6 +17,7 @@
 - better conversion to greyscale, thanks bkw
 - add vips_image_copy_memory(), improves stability with heavy threading
 - jpegsave supports new mozjpeg features [lovell]
+- add vips_vipsload(), vips_vipssave() ... why not
 
 26/3/15 started 7.42.4
 - im_maxpos_avg() avoids NaN

libvips/foreign/foreign.c

@@ -371,11 +371,12 @@ vips_foreign_init( VipsForeign *object )
  */
 
 static void *
-file_add_class( VipsForeignClass *file, GSList **files )
+file_add_class( VipsForeignClass *class, GSList **files )
 {
-	/* Append so we don't reverse the list of files.
+	/* Append so we don't reverse the list of files. Sort will not reorder
+	 * items of equal priority. 
 	 */
-	*files = g_slist_append( *files, file );
+	*files = g_slist_append( *files, class );
 
 	return( NULL );
 }
@@ -1681,6 +1682,56 @@ vips_foreign_operation_init( void )
 #endif /*HAVE_OPENEXR*/
 }
 
+/**
+ * vips_vipsload:
+ * @filename: file to load
+ * @out: decompressed image
+ * @...: %NULL-terminated list of optional named arguments
+ *
+ * Read in a vips image. 
+ *
+ * See also: vips_vipssave().
+ *
+ * Returns: 0 on success, -1 on error.
+ */
+int
+vips_vipsload( const char *filename, VipsImage **out, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, out );
+	result = vips_call_split( "vipsload", ap, filename, out );
+	va_end( ap );
+
+	return( result );
+}
+
+/**
+ * vips_vipssave:
+ * @in: image to save 
+ * @filename: file to write to 
+ * @...: %NULL-terminated list of optional named arguments
+ *
+ * Write @in to @filename in VIPS format.
+ *
+ * See also: vips_vipsload().
+ *
+ * Returns: 0 on success, -1 on error.
+ */
+int
+vips_vipssave( VipsImage *in, const char *filename, ... )
+{
+	va_list ap;
+	int result;
+
+	va_start( ap, filename );
+	result = vips_call_split( "vipssave", ap, in, filename );
+	va_end( ap );
+
+	return( result );
+}
+
 /**
  * vips_magickload:
  * @filename: file to load

libvips/include/vips/foreign.h

@@ -316,6 +316,11 @@ GType vips_foreign_save_get_type( void );
 const char *vips_foreign_find_save( const char *filename );
 const char *vips_foreign_find_save_buffer( const char *suffix );
 
+int vips_vipsload( const char *filename, VipsImage **out, ... )
+	__attribute__((sentinel));
+int vips_vipssave( VipsImage *in, const char *filename, ... )
+	__attribute__((sentinel));
+
 int vips_openslideload( const char *filename, VipsImage **out, ... )
 	__attribute__((sentinel));