[gimp] Issue #3758: fixes the build on mingw-w64.

[Jehan <jehanp src gnome org>]

commit 4cef17c7cfd1f4c6f6eba68d0d9b07a175c1f023
Author: lillolollo <4179-lillolollo users noreply gitlab gnome org>
Date:   Wed Aug 7 17:03:04 2019 +0000

    Issue #3758: fixes the build on mingw-w64.
    
    Fixes:
    > '_argc' undeclared (first use in this function)

 libgimp/gimp.h       | 2 +-
 libgimp/gimplegacy.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/libgimp/gimp.h b/libgimp/gimp.h
index 6bc74b6102..464c84dce8 100644
--- a/libgimp/gimp.h
+++ b/libgimp/gimp.h
@@ -112,7 +112,7 @@ G_BEGIN_DECLS
             int   nCmdShow)                             \
    {                                                    \
      return gimp_main (plug_in_type,                    \
-                       _argc, __argv);                  \
+                       __argc, __argv);                 \
    }                                                    \
                                                         \
    int                                                  \
diff --git a/libgimp/gimplegacy.h b/libgimp/gimplegacy.h
index 58624796c4..12a9e052fa 100644
--- a/libgimp/gimplegacy.h
+++ b/libgimp/gimplegacy.h
@@ -169,7 +169,7 @@ struct _GimpParam
             int   nCmdShow)                             \
    {                                                    \
      return gimp_main_legacy (&PLUG_IN_INFO,            \
-                              _argc, __argv);           \
+                              __argc, __argv);          \
    }                                                    \
                                                         \
    int                                                  \