dshow: Define STRSAFE_NO_DEPRECATE while building

The mingw dshow.h includes strsafe.h. Normally, strsafe.h deprecates
certain functions like strcpy and strcat, adding defines like
    #define strcpy strcpy_instead_use_StringCbCopyA_or_StringCchCopyA

libcxx contains code that declares "using ::strcpy;" and "using ::strcat;"
within a namespace, which breaks if strsafe.h has been included before.

Add this define to skip the deprecation defines in strsafe.h, fixing
buliding with libcxx.

modules/access/Makefile.am

@@ -157,6 +157,7 @@ endif
 
 libdshow_plugin_la_SOURCES = access/dshow/vlc_dshow.h access/dshow/dshow.cpp access/dshow/access.h \
 	access/dshow/filter.cpp access/dshow/filter.h access/dshow/crossbar.cpp
+libdshow_plugin_la_CPPFLAGS = $(AM_CPPFLAGS) -DSTRSAFE_NO_DEPRECATE
 libdshow_plugin_la_LIBADD = $(LIBCOM) -loleaut32 -luuid -lstrmiids -lksuser
 if HAVE_WIN32_DESKTOP
 access_LTLIBRARIES += libdshow_plugin.la