Log Message:
Update to 2.3.1. Changes since 2.3.0:

	Fix header loss problem in test mode.
	Fix bug #SF1808886: Handle missing or empty test inputs more
		gracefully.  Based on a patch from Kaspar Brand.
	Fix bug #SF1808881: Check various integer conversions for
		negative, overflow or inappropriate values.  Suggested
		by Kaspar Brand.
	Feature request #SF1809239: Restore performance of test mode on
		large messages.  Requested by Kaspar Brand.
	Patch #SF1811132: Include <stdlib.h> in test.c for malloc()
		prototype.  Patch from Daniel Black.
	BUILD: Patch #SF1810712: Correct default location for the Tre
		regular expression library.  Suggested by Daniel Black.