Test an edge case.

* subversion/tests/libsvn_fs/fs-test.c
  (almostmedium_file_integrity): New test, sibling to medium_file_integrity()
    and large_file_integrity().

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1486057 13f79535-47bb-0310-9956-ffa450edef68
Re-apply r1485848 with an extra fix that prevents the buffer overflow
plus is easier to understand.

* subversion/libsvn_subr/subst.c
  (translate_chunk): quickly scan for EOL if there is keyword substitution


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1486058 13f79535-47bb-0310-9956-ffa450edef68