mshtml: Write-strings warnings fix

[Andrew Talbot]

According to http://developer.mozilla.org/en/docs/XPCOM_API_Reference/,
the affected functions' string and wide-string parameters are "in strings",
which seems to mean that they are read-only, so may be constified. Hence,
this patch.
---
Changelog:
    mshtml: Write-strings warnings fix.

diff -urN a/dlls/mshtml/nsiface.idl b/dlls/mshtml/nsiface.idl
--- a/dlls/mshtml/nsiface.idl	2006-08-09 17:22:40.000000000 +0100
+++ b/dlls/mshtml/nsiface.idl	2006-08-17 22:23:56.000000000 +0100
@@ -34,9 +34,9 @@
 typedef nsIIDRef nsCIDRef;
 
 typedef void** nsQIResult;
-typedef LPSTR nsstring;
+typedef LPCSTR nscstring;
 typedef WCHAR PRUnichar;
-typedef LPWSTR nswstring;
+typedef LPCWSTR nscwstring;
 typedef ULONG PRUint32;
 typedef LONG PRInt32;
 typedef WORD PRUint16;