plug-ins: use GimpChannelOps in gfig rather than using a custom…

… SelectionType enum which lists anyway the same.

Fixes various warnings:

> warning: implicit conversion from ‘SelectionType’ to ‘GimpChannelOps’

plug-ins/gfig/gfig-dialog.c

@@ -112,13 +112,13 @@ SelectItVals selvals =
 
 selection_option selopt =
 {
-  ADD,          /* type */
-  FALSE,        /* Antia */
-  FALSE,        /* Feather */
-  10.0,         /* feather radius */
-  ARC_SEGMENT,  /* Arc as a segment */
-  FILL_PATTERN, /* Fill as pattern */
-  100.0,        /* Max opacity */
+  GIMP_CHANNEL_OP_ADD, /* type */
+  FALSE,               /* Antia */
+  FALSE,               /* Feather */
+  10.0,                /* feather radius */
+  ARC_SEGMENT,         /* Arc as a segment */
+  FILL_PATTERN,        /* Fill as pattern */
+  100.0,               /* Max opacity */
 };
 
 /* Should be kept in sync with GfigOpts */

plug-ins/gfig/gfig-types.h

@@ -32,14 +32,6 @@ typedef enum
   ISO_GRID
 } GridType;
 
-typedef enum
-{
-  ADD = 0,
-  SUBTRACT,
-  REPLACE,
-  INTERSECT
-} SelectionType;
-
 typedef enum
 {
   ARC_SEGMENT = 0,

plug-ins/gfig/gfig.h

@@ -48,13 +48,13 @@ typedef struct
 
 typedef struct
 {
-  SelectionType type;           /* ADD etc .. */
-  gint          antia;          /* Boolean for Antia */
-  gint          feather;        /* Feather it ? */
-  gdouble       feather_radius; /* Radius to feather */
-  ArcType       as_pie;         /* Arc type selection segment/sector */
-  FillType      fill_type;      /* Fill type for selection */
-  gdouble       fill_opacity;   /* You can guess this one */
+  GimpChannelOps type;           /* ADD etc .. */
+  gint           antia;          /* Boolean for Antia */
+  gint           feather;        /* Feather it ? */
+  gdouble        feather_radius; /* Radius to feather */
+  ArcType        as_pie;         /* Arc type selection segment/sector */
+  FillType       fill_type;      /* Fill type for selection */
+  gdouble        fill_opacity;   /* You can guess this one */
 } selection_option;
 
 void       object_start            (GdkPoint *pnt, gint);