themes: rename theme "Default" into "System".

Since we have many themes now, this new name better indicates that it
is meant to follow your desktop theme settings.
Also it will likely not remain the default theme.

app/config/gimpguiconfig.h

@@ -24,7 +24,7 @@
 #include "config/gimpdisplayconfig.h"
 
 
-#define GIMP_CONFIG_DEFAULT_THEME          "Default"
+#define GIMP_CONFIG_DEFAULT_THEME          "System"
 #define GIMP_CONFIG_DEFAULT_ICON_THEME     "Color"
 
 

configure.ac

@@ -2422,7 +2422,7 @@ icons/Legacy/Makefile
 icons/Symbolic/Makefile
 icons/Symbolic-Inverted/Makefile
 themes/Makefile
-themes/Default/Makefile
+themes/System/Makefile
 themes/Small/Makefile
 themes/Darker/Makefile
 themes/Dark/Makefile

docs/gimprc.5.in

@@ -850,7 +850,7 @@ Sets the theme search path.  This is a colon-separated list of folders to
 search.
 
 .TP
-(theme "Default")
+(theme "System")
 
 The name of the theme to use.  This is a string value.
 

etc/gimprc

@@ -667,7 +667,7 @@
 
 # The name of the theme to use.  This is a string value.
 # 
-# (theme "Default")
+# (theme "System")
 
 # Sets the icon theme search path.  This is a colon-separated list of folders
 # to search.

libgimpbase/gimpenv.c

@@ -814,7 +814,7 @@ gimp_gtkrc (void)
 
   if (! gimp_gtkrc_filename)
     gimp_gtkrc_filename = g_build_filename (gimp_data_directory (),
-                                            "themes", "Default", "gtkrc",
+                                            "themes", "System", "gtkrc",
                                             NULL);
 
   return gimp_gtkrc_filename;

themes/Makefile.am

@@ -1,3 +1,3 @@
 ## Process this file with automake to produce Makefile.in
 
-SUBDIRS = Default Small Darker Dark Gray Light Lighter
+SUBDIRS = Darker Dark Gray Light Lighter Small System

themes/System/Makefile.am

@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in
 
-themedatadir = $(gimpdatadir)/themes/Default
+themedatadir = $(gimpdatadir)/themes/System
 
 themedata_DATA = gtkrc