On the fsfs-format7 branch:  follow-up to r1442910 which accidentally
broke the tests.  Also, improve error checking.

* subversion/libsvn_subr/io.c
  (svn_io_file_aligned_seek): fix test for successful seek; use a common
  seek+getc sequence; don't bail out when accidentally reading beyond EOF

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-format7@1443171 13f79535-47bb-0310-9956-ffa450edef68