libgimpbase, plug-ins: fix all warnings to g_stat() calls.

The second parameter should be GStatBuf*, which will be defined to be
the right struct depending on the actual platform. Using `struct stat*`
was good on Linux but was outputting warnings on other platforms (at
least on Win32).

libgimpbase/gimpenv.c

@@ -1134,11 +1134,11 @@ gimp_path_free (GList *path)
 gchar *
 gimp_path_get_user_writable_dir (GList *path)
 {
-  GList       *list;
-  uid_t        euid;
-  gid_t        egid;
-  struct stat  filestat;
-  gint         err;
+  GList    *list;
+  uid_t     euid;
+  gid_t     egid;
+  GStatBuf  filestat;
+  gint      err;
 
   g_return_val_if_fail (path != NULL, NULL);
 

plug-ins/common/file-compressor.c

@@ -546,9 +546,9 @@ load_image (const CompressorEntry  *compressor,
 static gboolean
 valid_file (GFile *file)
 {
-  gchar       *filename;
-  struct stat  buf;
-  gboolean     valid;
+  gchar    *filename;
+  GStatBuf  buf;
+  gboolean  valid;
 
   filename = g_file_get_path (file);
   valid = g_stat (filename, &buf) == 0 && buf.st_size > 0;

plug-ins/common/mail.c

@@ -674,9 +674,9 @@ send_dialog (void)
 static gboolean
 valid_file (GFile *file)
 {
-  gchar       *filename;
-  struct stat  buf;
-  gboolean     valid;
+  gchar    *filename;
+  GStatBuf  buf;
+  gboolean  valid;
 
   filename = g_file_get_path (file);
   valid = g_stat (filename, &buf) == 0 && buf.st_size > 0;

plug-ins/file-psd/psd-load.c

@@ -119,13 +119,13 @@ load_image (GFile        *file,
             gboolean     *profile_loaded,
             GError      **load_error)
 {
-  gchar        *filename;
-  FILE         *f;
-  struct stat   st;
-  PSDimage      img_a;
-  PSDlayer    **lyr_a;
-  GimpImage    *image = NULL;
-  GError       *error = NULL;
+  gchar      *filename;
+  FILE       *f;
+  GStatBuf    st;
+  PSDimage    img_a;
+  PSDlayer  **lyr_a;
+  GimpImage  *image = NULL;
+  GError     *error = NULL;
 
   filename = g_file_get_path (file);
 

plug-ins/file-psd/psd-thumb-load.c

@@ -61,12 +61,12 @@ load_thumbnail_image (GFile   *file,
                       gint    *height,
                       GError **load_error)
 {
-  gchar       *filename;
-  FILE        *f;
-  struct stat  st;
-  PSDimage     img_a;
-  GimpImage   *image = NULL;
-  GError      *error = NULL;
+  gchar     *filename;
+  FILE      *f;
+  GStatBuf   st;
+  PSDimage   img_a;
+  GimpImage *image = NULL;
+  GError    *error = NULL;
 
   filename = g_file_get_path (file);