clar: stop including shellapi.h unnecessarily

The `shellapi.h` header was included as of
clar-test/clar@136e763211aa, to have
`SHFileOperation()` declared so that it could be called.

However, clar-test/clar@5ce31b69b525 removed
that call, and therefore that `#include <shellapi.h>` is unnecessary.

It is also unwanted in Git because this project uses a subset of Git for
Windows' SDK in its CI builds that (for bandwidth reasons) excludes tons
of header files, including `shellapi.h`.

So let's remove it.

Note: Since the `windows.h` header would include `shellapi.h` anyway, we
also define `WIN32_LEAN_AND_MEAN` to avoid this and similar other
unnecessary includes before including `windows.h`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: dscho

t/unit-tests/clar/clar.c

@@ -19,9 +19,9 @@
 #include <sys/stat.h>
 
 #ifdef _WIN32
+#	define WIN32_LEAN_AND_MEAN
 #	include <windows.h>
 #	include <io.h>
-#	include <shellapi.h>
 #	include <direct.h>
 
 #	define _MAIN_CC __cdecl