Accept a trailing space at end of PEM lines

With certs being copy-pasted from webmails and all, this will probably become
more and more common.

closes #226
diff --git a/ChangeLog b/ChangeLog
index 245670e..ec6892e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -14,6 +14,8 @@
      installed (found by Rawi666).
    * Fix compile error with armcc 5 with --gnu option.
 
+Changes
+   * The PEM parser now accepts a trailing space at end of lines (#226).
 
 = mbed TLS 2.0.0 released 2015-07-13