advpack: Cast-qual warnings fix

[Andrew Talbot]

Changelog:
    advpack: Cast-qual warnings fix.

diff -urN a/dlls/advpack/files.c b/dlls/advpack/files.c
--- a/dlls/advpack/files.c	2006-09-07 19:28:09.000000000 +0100
+++ b/dlls/advpack/files.c	2006-09-07 22:08:12.000000000 +0100
@@ -548,8 +548,8 @@
 static LPSTR convert_file_list(LPCSTR FileList, DWORD *dwNumFiles)
 {
     DWORD dwLen;
-    char *first = (char *)FileList;
-    char *last = (char *)FileList + strlen(FileList) - 1;
+    const char *first = FileList;
+    const char *last = FileList + strlen(FileList) - 1;
     LPSTR szConvertedList, temp;
     
     /* any number of these chars before the list is OK */