Fix issue on test on Windows with Python 3.

(cherry-pick of hunks from r1822485 and its fix r1822486, on branch swig-py3) 

* build/generator/gen_base.py
  (IncludeDependencyInfo._scan_for_includes): Ensure file data is
   properly encoded as UTF8. (r1822485, r1822486)

* build/generator/gen_win.py
  (WinGeneratorBase.makeguid): Ensure data input to hashlib is binary
   and not Unicode. (r1822485)

* build/generator/gen_win_dependencies.py
  (GenDependenciesBase._find_swig,
   GenDependenciesBase._find_jdk): Ensure output from subprocess is
   properly decoded. (r1822485)

Index: build/generator/gen_base.py
===================================================================
--- build/generator/gen_base.py	(revision 1868582)
+++ build/generator/gen_base.py	(working copy)
@@ -1273,7 +1273,8 @@
     Return a dictionary with included full file names as keys and None as
     values."""
     hdrs = { }
-    for line in fileinput.input(fname):
+
+    for line in fileinput.FileInput(fname, openhook=fileinput.hook_encoded("utf-8")):
       match = self._re_include.match(line)
       if not match:
         continue
Index: build/generator/gen_win.py
===================================================================
--- build/generator/gen_win.py	(revision 1868582)
+++ build/generator/gen_win.py	(working copy)
@@ -158,6 +158,13 @@
     ### implement this from scratch using the algorithms described in
     ### http://www.webdav.org/specs/draft-leach-uuids-guids-01.txt
 
+    # Ensure data is in byte representation.  If it doesn't have an encode
+    # attribute, assume it is already in the correct form.
+    try:
+      data = data.encode('utf8')
+    except AttributeError:
+      pass
+
     myhash = hashlib_md5(data).hexdigest()
 
     guid = ("{%s-%s-%s-%s-%s}" % (myhash[0:8], myhash[8:12],
Index: build/generator/gen_win_dependencies.py
===================================================================
--- build/generator/gen_win_dependencies.py	(revision 1868582)
+++ build/generator/gen_win_dependencies.py	(working copy)
@@ -1080,7 +1080,7 @@
       outfp = subprocess.Popen([os.path.join(jdk_path, 'bin', 'javac.exe'),
                                '-version'], stdout=subprocess.PIPE,
                                stderr=subprocess.STDOUT).stdout
-      line = outfp.read()
+      line = outfp.read().decode('utf8')
       if line:
         vermatch = re.search(r'(([0-9]+(\.[0-9]+)+)(_[._0-9]+)?)', line, re.M)
       else:
@@ -1138,7 +1138,7 @@
     try:
       fp = subprocess.Popen([self.swig_exe, '-version'],
                             stdout=subprocess.PIPE).stdout
-      txt = fp.read()
+      txt = fp.read().decode('utf8')
       if txt:
         vermatch = re.search(r'^SWIG\ Version\ (\d+)\.(\d+)\.(\d+)', txt, re.M)
       else:
@@ -1166,7 +1166,7 @@
     try:
       fp = subprocess.Popen([self.swig_exe, '-swiglib'],
                             stdout=subprocess.PIPE).stdout
-      lib_dir = fp.readline().strip()
+      lib_dir = fp.readline().decode('utf8').strip()
       fp.close()
     except OSError:
       lib_dir = None