[LyX/2.3-staging] Use c-style cast as in original

[Georg Baum]

commit 7c2d844a68fc54754494dd83398c3e0db3144558
Author: Georg Baum <b...@lyx.org>
Date:   Thu May 5 19:28:11 2016 +0200

    Use c-style cast as in original
    
    static_cast does not work

diff --git a/src/support/filetools.cpp b/src/support/filetools.cpp
index 657343f..a72c93e 100644
--- a/src/support/filetools.cpp
+++ b/src/support/filetools.cpp
@@ -1065,7 +1065,7 @@ cmd_ret const runCommand(string const & cmd)
                                0, 0, &startup, &process)) {
 
                        CloseHandle(process.hThread);
-                       int fno = _open_osfhandle(static_cast<intptr_t>(in), 
_O_RDONLY);
+                       int fno = _open_osfhandle((intptr_t)in, _O_RDONLY);
                        CloseHandle(out);
                        inf = _fdopen(fno, "r");
                }