deprecate vips_popen()

it didn't work well on win, and we no longer use it anyway

libvips/deprecated/vips7compat.c

@@ -5692,3 +5692,14 @@ vips_get_option_group( void )
 
 	return( option_group );
 }
+
+/* We used to use this for system() back in the day. But it's awkward to make
+ * it work properly on win32, so this is nonw deprecated.
+ */
+FILE *
+vips_popenf( const char *fmt, const char *mode, ... )
+{
+        vips_error( "popenf", "%s", _( "deprecated" ) );
+        return( NULL );
+}
+

libvips/include/vips/util.h

@@ -286,8 +286,6 @@ int vips_mkdirf( const char *name, ... )
 int vips_rmdirf( const char *name, ... )
 	__attribute__((format(printf, 1, 2)));
 int vips_rename( const char *old_name, const char *new_name );
-FILE *vips_popenf( const char *fmt, const char *mode, ... )
-	__attribute__((format(printf, 1, 3)));
 
 /** 
  * VipsToken:

libvips/include/vips/vips7compat.h

@@ -1221,6 +1221,9 @@ GOptionGroup *vips_get_option_group( void );
  */
 VipsWindow *vips_window_ref( VipsImage *im, int top, int height );
 
+FILE *vips_popenf( const char *fmt, const char *mode, ... )
+	__attribute__((format(printf, 1, 3)));
+
 /* This stuff is very, very old and should not be used by anyone now.
  */
 #ifdef VIPS_ENABLE_ANCIENT

libvips/iofuncs/util.c

@@ -1191,40 +1191,6 @@ vips_isdirf( const char *name, ... )
 	return( result ); 
 }
 
-#ifdef OS_WIN32
-#ifndef popen
-#define popen(b,m) _popen(b,m)
-#endif
-#ifndef pclose
-#define pclose(f) _pclose(f)
-#endif
-#endif /*OS_WIN32*/
-
-/* Do popen(), with printf-style args.
- */
-FILE *
-vips_popenf( const char *fmt, const char *mode, ... )
-{
-        va_list args;
-	char buf[VIPS_PATH_MAX];
-	FILE *fp;
-
-        va_start( args, mode );
-        (void) vips_vsnprintf( buf, VIPS_PATH_MAX, fmt, args );
-        va_end( args );
-
-#ifdef DEBUG
-	printf( "vips_popenf: running: %s\n", buf );
-#endif /*DEBUG*/
-
-        if( !(fp = popen( buf, mode )) ) {
-		vips_error( "popenf", "%s", strerror( errno ) );
-		return( NULL );
-	}
-
-	return( fp );
-}
-
 /* Make a directory.
  */
 int

libvips/iofuncs/vips.c

@@ -94,10 +94,6 @@
 #include <expat.h>
 #include <errno.h>
 
-#ifdef OS_WIN32
-#include <windows.h>
-#endif /*OS_WIN32*/
-
 #include <vips/vips.h>
 #include <vips/internal.h>
 #include <vips/debug.h>