Windows fix: normalizes extra_incdir, universal_newlines on preprocessor output.

When input is a filename without directory, the dirname is empty, which inserts `-I `, instead of ` -I .`, which breaks the command.
Remedied with os.path.normpath

On Windows with MinGW gcc, preprocessor output has Windows newlines, which pycparser can't handle.
Remedied by universal_newlines=True for subprocess.

Py3: universal_newlines=True changes `subprocess.communicate` to take and return strings instead of bytes. Adjusted for this.
Current master reads input headers as bytes. This causes `code.encode` to fail. Changed `cli` to open files as text fixes this.

Tested with `test.py` on Python 2.7 and 3.5 on Windows 10.

Author: Per Rosengren

autopxd/__init__.py

@@ -303,16 +303,15 @@ def lines(self):
 
 
 def preprocess(code, extra_cpp_args=[]):
-    proc = subprocess.Popen([
-        'cpp', '-nostdinc', '-D__attribute__(x)=', '-I', BUILTIN_HEADERS_DIR,
-    ] + extra_cpp_args + ['-'], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
-    result = []
-    result.append(proc.communicate(input=code.encode('utf-8'))[0])
-    while proc.poll() is None:
-        result.append(proc.communicate()[0])
+    proc = subprocess.Popen(
+        ['cpp', '-nostdinc', '-D__attribute__(x)=',
+            '-I', BUILTIN_HEADERS_DIR] +
+        extra_cpp_args + ['-'],
+        stdin=subprocess.PIPE, stdout=subprocess.PIPE, universal_newlines=True)
+    result = proc.communicate(input=code)[0]
     if proc.returncode:
         raise Exception('Invoking C preprocessor failed')
-    return b''.join(result).decode('utf-8')
+    return result
 
 
 def parse(code, extra_cpp_args=[]):
@@ -328,14 +327,14 @@ def parse(code, extra_cpp_args=[]):
 
 
 def translate(code, hdrname, extra_cpp_args=[]):
-    extra_incdir = os.path.dirname(hdrname)
+    extra_incdir = os.path.normpath(os.path.dirname(hdrname))
     p = AutoPxd(hdrname)
     p.visit(parse(code, extra_cpp_args=['-I', extra_incdir]))
     return str(p)
 
 
 @click.command()
-@click.argument('infile', type=click.File('rb'), default=sys.stdin)
-@click.argument('outfile', type=click.File('wb'), default=sys.stdout)
+@click.argument('infile', type=click.File(), default=sys.stdin)
+@click.argument('outfile', type=click.File('wt'), default=sys.stdout)
 def cli(infile, outfile):
     outfile.write(translate(infile.read(), infile.name))