[gimp] libgimp: add some (nullable) annotation and fix some comments.

[Jehan <jehanp src gnome org>]

commit 8f79ddbfe021be2bda8b3bd2cb909eda1399584c
Author: Jehan <jehan girinstud io>
Date:   Fri Aug 9 12:48:41 2019 +0200

    libgimp: add some (nullable) annotation and fix some comments.

 libgimp/gimp.c | 4 ++--
 libgimp/gimp.h | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/libgimp/gimp.c b/libgimp/gimp.c
index ac835cdd0a..2574f2119d 100644
--- a/libgimp/gimp.c
+++ b/libgimp/gimp.c
@@ -631,7 +631,7 @@ _gimp_main_internal (GType                 plug_in_type,
  * This function returns the plug-in's #GimpPlugIn instance, which can
  * exist exactly once per running plug-in program.
  *
- * Returns: (transfer none): The plug-in's #GimpPlugIn singleton, or %NULL.
+ * Returns: (transfer none) (nullable): The plug-in's #GimpPlugIn singleton, or %NULL.
  *
  * Since: 3.0
  **/
@@ -647,7 +647,7 @@ gimp_get_plug_in (void)
  * This function returns the plug-in's #GimpPDB instance, which can
  * exist exactly once per running plug-in program.
  *
- * Returns: (transfer none): The plug-in's #GimpPDB singleton, or %NULL.
+ * Returns: (transfer none) (nullable): The plug-in's #GimpPDB singleton, or %NULL.
  *
  * Since: 3.0
  **/
diff --git a/libgimp/gimp.h b/libgimp/gimp.h
index 464c84dce8..00edc46eb8 100644
--- a/libgimp/gimp.h
+++ b/libgimp/gimp.h
@@ -147,12 +147,12 @@ gint                gimp_main                 (GType  plug_in_type,
  */
 GimpPlugIn        * gimp_get_plug_in          (void);
 
-/* Return the GimpPlugIn singleton of this plug-in process
+/* Return the GimpPDB singleton of this plug-in process
  */
 GimpPDB           * gimp_get_pdb              (void);
 
 /* Forcefully causes the gimp library to exit and
- *  close down its connection to main gimp application.
+ * close down its connection to main gimp application.
  */
 void                gimp_quit                 (void) G_GNUC_NORETURN;