Make keysymtab static and const

Static to avoid namespace polution, and const so that it can be
shared among instances.
diff --git a/vncviewer/keysym2ucs.c b/vncviewer/keysym2ucs.c
index d12eb49..4e3dca2 100644
--- a/vncviewer/keysym2ucs.c
+++ b/vncviewer/keysym2ucs.c
@@ -37,7 +37,9 @@
 struct codepair {
   unsigned short keysym;
   unsigned short ucs;
-} keysymtab[] = {
+};
+
+static const struct codepair keysymtab[] = {
   { 0x01a1, 0x0104 }, /*                     Aogonek Ą LATIN CAPITAL LETTER A WITH OGONEK */
   { 0x01a2, 0x02d8 }, /*                       breve ˘ BREVE */
   { 0x01a3, 0x0141 }, /*                     Lstroke Ł LATIN CAPITAL LETTER L WITH STROKE */