Security update for mercurial (moderate)

This update for mercurial fixes the following issues:

Security issues fixed:

• CVE-2018-13348: Fix the mpatch_decode function in mpatch.c that
  mishandles certain situations where there should be at least 12 bytes
  remaining after thecurrent position in the patch data (boo#1100353).
• CVE-2018-13347: Fix mpatch.c that mishandles integer addition and
  subtraction (boo#1100355).
• CVE-2018-13346: Fix the mpatch_apply function in mpatch.c that
  incorrectly proceeds in cases where the fragment start is past the end
  of the original data (boo#1100354).