chore: import upstream snapshot with attribution

vendored/tre/regex.h

@@ -0,0 +1,48 @@
+/*
+  regex.h - TRE legacy API
+
+  This software is released under a BSD-style license.
+  See the file LICENSE for details and copyright.
+
+  This header is for source level compatibility with old code using
+  the <tre/regex.h> header which defined the TRE API functions without
+  a prefix.  New code should include <tre/tre.h> instead.
+
+*/
+
+#ifndef TRE_REXEX_H
+#define TRE_REGEX_H 1
+
+#ifdef USE_LOCAL_TRE_H
+/* Use the header(s) from the TRE package that this file is part of.
+   (Yes, this file is in local_include too, but the explict path
+   means there is no way to get a system tre.h by accident.) */
+#include "tre.h"
+#else
+/* Use the header(s) from an installed version of the TRE package
+   (so that this application matches the installed libtre),
+   not the one(s) in the local_includes directory. */
+#include <tre/tre.h>
+#endif
+
+#ifndef TRE_USE_SYSTEM_REGEX_H
+#define regcomp	   tre_regcomp
+#define regerror   tre_regerror
+#define regexec	   tre_regexec
+#define regfree	   tre_regfree
+#endif /* TRE_USE_SYSTEM_REGEX_H */
+
+#define regacomp   tre_regacomp
+#define regaexec   tre_regaexec
+#define regancomp  tre_regancomp
+#define reganexec  tre_reganexec
+#define regawncomp tre_regawncomp
+#define regawnexec tre_regawnexec
+#define regncomp   tre_regncomp
+#define regnexec   tre_regnexec
+#define regwcomp   tre_regwcomp
+#define regwexec   tre_regwexec
+#define regwncomp  tre_regwncomp
+#define regwnexec  tre_regwnexec
+
+#endif /* TRE_REGEX_H */