[IO] implement binary slurp

also coerce filename to Str before unboxing. Should avoid the LTA error message
reported in RT #114124

src/core/IO.pm

@@ -96,7 +96,7 @@ class IO does IO::FileTestable {
         nqp::bindattr(self, IO, '$!PIO',
              $path eq '-'
                 ?? ( $w || $a ?? pir::getstdout__P() !! pir::getstdin__P() )
-                !! nqp::open(nqp::unbox_s($path), nqp::unbox_s($mode))
+                !! nqp::open(nqp::unbox_s($path.Str), nqp::unbox_s($mode))
         );
         $!path = $path;
         $!chomp = $chomp;
@@ -354,12 +354,25 @@ multi sub close($fh) {
 }
 
 proto sub slurp(|$) { * }
-multi sub slurp($filename) {
-    my $handle = open($filename, :r);
-    my $contents = $handle.slurp();
-    $handle.close();
-    $contents
+multi sub slurp($filename, :$bin = False) {
+    my $handle = open($filename, :r, :$bin);
+    if $bin {
+        my $Buf = Buf.new();
+        loop {
+            my $current  = $handle.read(10_000);
+            $Buf ~= $current;
+            last if $current.bytes == 0;
+        }
+        $handle.close;
+        $Buf;
+    }
+    else {
+        my $contents = $handle.slurp();
+        $handle.close();
+        $contents
+    }
 }
+
 multi sub slurp(IO $io = $*ARGFILES) {
     $io.slurp;
 }