add md5sum tool using MappedByteArray from Kapace++'s gci task

examples/pir/md5sum.pir

@@ -0,0 +1,21 @@
+.sub main
+      .param pmc argv
+      load_bytecode "Digest/MD5.pbc"
+      .local pmc mba
+      .local string filename
+
+      set filename, argv[1]
+      $S0 = "Creating new MappedByteArray, and opening " . filename
+      say $S0
+      mba = new 'MappedByteArray'
+      mba.'open'(filename)
+
+      say 'getting the data from the Mapped Byte Array...'
+      $I1 = elements mba
+      $S0 = mba.'get_string'(0, $I1, 'binary')
+
+      $P1 = _md5sum($S0)
+      $S0 = _md5_hex($P1)
+      say $S0
+  .end
+