Update to 2.5.2. Changes since 2.5.1:

• Patch OOB write in content-line analyzer:
  
  https://bro-tracker.atlassian.net/browse/BIT-1856
  
  A combination of packets can trigger an out of bound write of '0' byte in the content-line analyzer.

Reviewed by: ler (mentor)
Approved by: ler (mentor)
Differential Revision: https://reviews.freebsd.org/D12754