building: build inotify for sys.platform='linux*'

If Python interpreter was built under Linux 3.x kernel, it reports
sys.platform to be 'linux3' (it is fixed for Python 3, but not for 2.x).
This cancels building inotify extension, which was built only for 'linux2'
platform. Improved test checks if sys.platform begins with 'linux', and together
with test for kernel version to be greater than 2.6 it seems to cover all known
cases.

contrib/setup3k.py

@@ -309,7 +309,7 b" if sys.platform == 'win32' and sys.versi"
 else:
     extmodules.append(Extension('mercurial.osutil', ['mercurial/osutil.c']))
 
-if sys.platform == 'linux2' and os.uname()[2] > '2.6':
+if sys.platform.startswith('linux') and os.uname()[2] > '2.6':
     # The inotify extension is only usable with Linux 2.6 kernels.
     # You also need a reasonably recent C library.
     # In any case, if it fails to build the error will be skipped ('optional').

hgext/inotify/server.py

@@ -443,7 +443,7 b' class socketlistener(object):'
             if err.args[0] != errno.EPIPE:
                 raise
 
-if sys.platform == 'linux2':
+if sys.platform.startswith('linux'):
     import linuxserver as _server
 else:
     raise ImportError

setup.py

@@ -366,7 +366,7 b' else:'
     extmodules.append(Extension('mercurial.osutil', ['mercurial/osutil.c'],
                                 extra_link_args=osutil_ldflags))
 
-if sys.platform == 'linux2' and os.uname()[2] > '2.6':
+if sys.platform.startswith('linux') and os.uname()[2] > '2.6':
     # The inotify extension is only usable with Linux 2.6 kernels.
     # You also need a reasonably recent C library.
     # In any case, if it fails to build the error will be skipped ('optional').