add im_init_world() entry point

C++ programs need this as a function rather than just a macro, see
VImage.h

thanks Phil for finding this

ChangeLog

@@ -1,3 +1,6 @@
+15/11/13	started 7.36.4
+- improve compat with im_init_world()
+
 18/10/13	started 7.36.3
 - fix compiler warnings in ubuntu 13.10
 - reverse similarity rotation direction to match the convention used 

configure.ac

@@ -2,7 +2,7 @@
 
 # also update the version number in the m4 macros below
 
-AC_INIT([vips], [7.36.3], [vipsip@jiscmail.ac.uk])
+AC_INIT([vips], [7.36.4], [vipsip@jiscmail.ac.uk])
 # required for gobject-introspection
 AC_PREREQ(2.62)
 
@@ -17,7 +17,7 @@ AC_CONFIG_MACRO_DIR([m4])
 # user-visible library versioning
 m4_define([vips_major_version], [7])
 m4_define([vips_minor_version], [36])
-m4_define([vips_micro_version], [3])
+m4_define([vips_micro_version], [4])
 m4_define([vips_version],
           [vips_major_version.vips_minor_version.vips_micro_version])
 
@@ -37,7 +37,7 @@ VIPS_VERSION_STRING=$VIPS_VERSION-`date`
 #   binary interface changes not backwards compatible?: reset age to 0
 
 LIBRARY_CURRENT=35
-LIBRARY_REVISION=3
+LIBRARY_REVISION=4
 LIBRARY_AGE=0
 
 # patched into include/vips/version.h

libvips/deprecated/vips7compat.c

@@ -232,6 +232,17 @@ im_init( const char *filename )
 	return( image );
 }
 
+/* We can't do this with a rename macro since the C++ interface needs
+ * this entrypoint, see VImage.h.
+ *
+ * As a result our fancy ABI check will not work with the vips7 interface.
+ */
+int
+im_init_world( const char *argv0 )
+{
+	return( vips_init( argv0 ) );
+}
+
 /* Prettyprint various header fields. Just for vips7 compat, use
  * vips_enum_value() instead.
  */

libvips/include/vips/vips7compat.h

@@ -32,7 +32,7 @@
  */
 
 #ifndef VIPS_VIPS7COMPAT_H
-#define VIPS_VIP7COMPATS_H
+#define VIPS_VIPS7COMPAT_H
 
 #ifdef __cplusplus
 extern "C" {
@@ -203,7 +203,6 @@ extern "C" {
 #define im_get_argv0 vips_get_argv0
 #define im_version_string vips_version_string
 #define im_version vips_version
-#define im_init_world vips_init
 #define im_get_option_group vips_get_option_group
 #define im_guess_prefix vips_guess_prefix
 #define im_guess_libdir vips_guess_libdir
@@ -256,6 +255,8 @@ extern "C" {
 /* Compat functions.
  */
 
+int im_init_world( const char *argv0 ); 
+
 VipsImage *im_open( const char *filename, const char *mode );
 
 VipsImage *im_open_local( VipsImage *parent,