Fix test suite failures under Ubuntu 12.04 due to multiarch.

Updated loader as libc and libm loading was failing due to looking
in wrong directories.

Tested platform:

    $ cat /etc/*elease
    DISTRIB_ID=Ubuntu
    DISTRIB_RELEASE=12.04
    DISTRIB_CODENAME=precise
    DISTRIB_DESCRIPTION="Ubuntu 12.04.1 LTS"

ctypesgencore/libraryloader.py

@@ -33,6 +33,7 @@
 # ----------------------------------------------------------------------------
 
 import os.path, re, sys, glob
+import platform
 import ctypes
 import ctypes.util
 
@@ -167,7 +168,21 @@ def _create_ld_so_cache(self):
         try: directories.extend([dir.strip() for dir in open('/etc/ld.so.conf')])
         except IOError: pass
 
-        directories.extend(['/lib', '/usr/lib', '/lib64', '/usr/lib64'])
+        unix_lib_dirs_list = ['/lib', '/usr/lib', '/lib64', '/usr/lib64']
+        if sys.platform.startswith('linux'):
+            # Try and support multiarch work in Ubuntu
+            # https://wiki.ubuntu.com/MultiarchSpec
+            bitage = platform.architecture()[0]
+            if bitage.startswith('32'):
+                # Assume Intel/AMD x86 compat
+                unix_lib_dirs_list += ['/lib/i386-linux-gnu', '/usr/lib/i386-linux-gnu']
+            elif bitage.startswith('64'):
+                # Assume Intel/AMD x86 compat
+                unix_lib_dirs_list += ['/lib/x86_64-linux-gnu', '/usr/lib/x86_64-linux-gnu']
+            else:
+                # guess...
+                unix_lib_dirs_list += glob.glob('/lib/*linux-gnu')
+        directories.extend(unix_lib_dirs_list)
 
         cache = {}
         lib_re = re.compile(r'lib(.*)\.s[ol]')