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
Change-Id: If0b7f59a59824e30aa0c33dad76c7a44932180de