patch 8.2.0872: XIM code is mixed with multi-byte code

Problem:    XIM code is mixed with multi-byte code.
Solution:   Move the XIM code to a separate file. (Yegappan Lakshmanan,
            closes #6177)
diff --git a/Filelist b/Filelist
index a0f9877..2dbb2d3 100644
--- a/Filelist
+++ b/Filelist
@@ -419,6 +419,7 @@
 		src/gui_gtk_x11.c \
 		src/gui_gtk_res.xml \
 		src/gui_motif.c \
+		src/gui_xim.c \
 		src/gui_xmdlg.c \
 		src/gui_xmebw.c \
 		src/gui_xmebw.h \
@@ -442,6 +443,7 @@
 		src/proto/gui_gtk_x11.pro \
 		src/proto/gui_gtk_gresources.pro \
 		src/proto/gui_motif.pro \
+		src/proto/gui_xim.pro \
 		src/proto/gui_xmdlg.pro \
 		src/proto/gui_x11.pro \
 		src/proto/if_xcmdsrv.pro \