unix-ffi/machine: Use libc if librt is not present.

Newer implementations of libc integrate the functions from librt, for
example glibc since 2.17 and uClibc-ng.  So if the librt.so cannot be
loaded, it can be assumed that libc contains the expected functions.

Signed-off-by: Bas van Doren <basvdoren@gmail.com>

unix-ffi/machine/machine/timer.py

@@ -5,7 +5,10 @@ import os
 from signal import *
 
 libc = ffilib.libc()
-librt = ffilib.open("librt")
+try:
+    librt = ffilib.open("librt")
+except OSError as e:
+    librt = libc
 
 CLOCK_REALTIME = 0
 CLOCK_MONOTONIC = 1

unix-ffi/machine/manifest.py

@@ -1,4 +1,4 @@
-metadata(version="0.2.1")
+metadata(version="0.2.2")
 
 # Originally written by Paul Sokolovsky.