kernel32: Constify a variable

[Andrew Talbot]

Changelog:
    kernel32: Constify a variable.

diff -urN a/dlls/kernel32/win87em.c b/dlls/kernel32/win87em.c
--- a/dlls/kernel32/win87em.c	2006-10-13 11:27:19.000000000 +0100
+++ b/dlls/kernel32/win87em.c	2007-02-15 21:19:12.000000000 +0000
@@ -53,7 +53,7 @@
 static WORD StatusWord_1 = 0x000b;
 static WORD StatusWord_2 = 0;
 static WORD StatusWord_3 = 0;
-static WORD StackTop = 175;
+static const WORD StackTop = 175;
 static WORD StackBottom = 0;
 static WORD Inthandler02hVar = 1;