Remove libsigchain from LD_PRELOADS

  Link sigchain.cc statically with dalvikvm, app_process,
  surfaceflinger, dex2oat, patchoat and objdump.

  Replace libsigchain.so with dummy implementaions to avoid
  situations when it is used incorrectly.

Bug: 15345057
Bug: 15426766

(cherry picked from commit f57874dd)

Change-Id: I07fe3ca4eeef423d78d7e9a639f03fc59aae3b29