[Build] Add a patch to check whether we have .NET 4.6 at build time.

Author: Therzok

configure.in.in

@@ -106,9 +106,15 @@ OFF_T_FLAGS="-define:OFF_T_$ac_cv_sizeof_off_t"
 AC_SUBST(OFF_T_FLAGS)
 
 MONO_REQUIRED_VERSION=1.0
+MONO_NO_NET_4_6=4.4
 PKG_CHECK_MODULES(MONO_DEPENDENCY, mono >= $MONO_REQUIRED_VERSION, has_mono=true, has_mono=false)
 if test "x$has_mono" = "xfalse" ; then
 	PKG_CHECK_MODULES(MONO_DEPENDENCY, mono-2 >= $MONO_REQUIRED_VERSION, has_mono=true, has_mono=false)
+	if "x$has_mono" = "xtrue" ; then
+		PKG_CHECK_MODULES(MONO_DEPENDENCY, mono < $MONO_NO_NET_4_6, missing_net_4_6=true, missing_net_4_6=false)
+	fi
+else
+	PKG_CHECK_MODULES(MONO_DEPENDENCY, mono < $MONO_NO_NET_4_6, missing_net_4_6=true, missing_net_4_6=false)
 fi
 
 AC_PATH_PROG(GACUTIL, gacutil, no)
@@ -224,6 +230,9 @@ AM_CONDITIONAL(ENABLE_MONOGETOPTIONS, test "x$has_mono" = "xtrue")
 
 CSFLAGS="$DEBUG_FLAGS $CSDEFINES $WIN64DEFINES -unsafe"
 
+if text "x$missing_net_4_6" = "xyes" ; then
+  CSFLAGS="$CSFLAGS -define:MISSING_NET_4_6"
+fi
 PKG_CHECK_MODULES(GLIB_2_31,
   glib-2.0 >= 2.31,
   HAVE_GLIB_2_31_OR_HIGHER=yes, HAVE_GLIB_2_31_OR_HIGHER=no)

glib/Marshaller.cs

@@ -88,15 +88,19 @@ static string Utf8PtrToStringFast (IntPtr ptr, int len)
 			}
 		}
 
+#if !MISSING_NET_4_6
 		static bool hasFastGetStringOverload = typeof (System.Text.Encoding).GetMethod ("GetString", new [] { typeof (byte*), typeof (int) }) != null;
+#endif
 		public static string Utf8PtrToString (IntPtr ptr) 
 		{
 			if (ptr == IntPtr.Zero)
 				return null;
 
 			int len = (int) (uint)glibsharp_strlen (ptr);
+#if !MISSING_NET_4_6
 			if (hasFastGetStringOverload)
 				return Utf8PtrToStringFast (ptr, len);
+#endif
 
 			byte [] bytes = new byte [len];
 			Marshal.Copy (ptr, bytes, 0, len);