Fix win32 'python setup.py ...' build  --  use double quotes

When on win32, it makes a difference, whether '...' or "..." is used in shell,
consider:

  C:\>pkg-config --print-errors 'cairo >= 1.4.12'
  Package 'cairo was not found in the pkg-config search path.
  Perhaps you should add the directory containing `'cairo.pc'
  to the PKG_CONFIG_PATH environment variable
  No package ''cairo' found

v.s.

  C:\>pkg-config --print-errors "cairo >= 1.4.12"
  C:\>pkg-config --print-errors "cairo >= 1.8.12"
  Requested 'cairo >= 1.8.12' but version of cairo is 1.6.4


So it is important to use double quotes.

diff -u -r1.23 setup.py
--- setup.py	12 May 2008 12:06:37 -0000	1.23
+++ setup.py	27 May 2008 11:34:21 -0000
@@ -20,7 +20,7 @@
     return pipe
 
 def pkg_config_version_check(pkg, version):
-    pipe = call("pkg-config --print-errors --exists '%s >= %s'" %
+    pipe = call("pkg-config --print-errors --exists \"%s >= %s\"" %
                 (pkg, version))
     if pipe.returncode == 0:
         print '%s >= %s detected' % (pkg, version)