Add ChangeLog

CHANGELOG.md

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+# Hyperscan Change Log
+
+This is a list of notable changes to Hyperscan, in reverse chronological order.
+
+## [4.1.0] 2015-12-18
+- Update version of PCRE used by testing tools as a syntax and semantic
+  reference to PCRE 8.38.
+- Small updates to fix warnings identified by Coverity.
+- Clean up and unify exception handling behaviour across GPR and SIMD NFA
+  models.
+- Fix bug in handling of bounded repeat triggers with large gaps between them
+  for sparse repeat model.
+- Correctly reject POSIX collating elements (`[.ch.]`, `[=ch=]`) in the parser.
+  These are not supported by Hyperscan.
+- Add support for quoted sequences (`\Q...\E`) inside character classes.
+- Simplify FDR literal matcher runtime by removing some static specialization.
+- Fix handling of the POSIX `[:graph:]`, `[:print:]` and `[:punct:]` character
+  classes to match the behaviour of PCRE 8.38 in both standard operation and
+  with the UCP flag set. (Note: some bugs were fixed in this area in PCRE
+  8.38.) Previously Hyperscan's behaviour was the same as versions of PCRE
+  before 8.34.
+- Improve performance when compiling pattern sets that include a large number
+  of similar bounded repeat constructs. (github issue #9)
+
+## [4.0.1] 2015-10-30
+- Minor cleanups to test code.
+- CMake and other build system improvements.
+- API update: allow `hs_reset_stream()` and `hs_reset_and_copy_stream()` to be
+  supplied with a NULL scratch pointer if no matches are required. This is in
+  line with the behaviour of `hs_close_stream()`.
+- Disallow bounded repeats with a very large minimum repeat but no maximum,
+  i.e. {N,} for very large N.
+- Reduce compile memory usage in literal set explansion for some large cases.
+
+## [4.0.0] 2015-10-20
+- Original release of Hyperscan as open-source software.