Make Unicode const strings static so they are not copied to the stack
each time we enter the function.

diff --git a/dlls/uxtheme/system.c b/dlls/uxtheme/system.c
index 2ffb402..a68d0be 100644
--- a/dlls/uxtheme/system.c
+++ b/dlls/uxtheme/system.c
@@ -191,13 +191,13 @@
  */
 void UXTHEME_InitSystem(HINSTANCE hInst)
 {
-    const WCHAR szWindowTheme[] = {
+    static const WCHAR szWindowTheme[] = {
         'u','x','_','t','h','e','m','e','\0'
     };
-    const WCHAR szSubAppName[] = {
+    static const WCHAR szSubAppName[] = {
         'u','x','_','s','u','b','a','p','p','\0'
     };
-    const WCHAR szSubIdList[] = {
+    static const WCHAR szSubIdList[] = {
         'u','x','_','s','u','b','i','d','l','s','t','\0'
     };