vre: New VRE_capture() function

It's a thin wrapper on top of vre_capture() that returns the number of
groups captured during a match.

Now that txt appears in vre.h we need vdef.h anywhere the former is
included. There was one generated file where that wasn't the case.

Closes #3655

include/vre.h

@@ -60,6 +60,8 @@ vre_t *VRE_export(const vre_t *, size_t *);
 int VRE_error(struct vsb *, int err);
 int VRE_match(const vre_t *code, const char *subject, size_t length,
     int options, const volatile struct vre_limits *lim);
+int VRE_capture(vre_t *code, const char *subject, size_t length, int options,
+    txt *groups, size_t count, const volatile struct vre_limits *lim);
 int VRE_sub(const vre_t *code, const char *subject, const char *replacement,
     struct vsb *vsb, const volatile struct vre_limits *lim, int all);
 void VRE_free(vre_t **);

lib/libvarnish/vre.c

@@ -243,6 +243,29 @@ VRE_match(const vre_t *code, const char *subject, size_t length,
 	    NULL, NULL, NULL));
 }
 
+int
+VRE_capture(vre_t *code, const char *subject, size_t length, int options,
+    txt *groups, size_t count, const volatile struct vre_limits *lim)
+{
+	int i;
+
+	CHECK_OBJ_NOTNULL(code, VRE_MAGIC);
+	AN(subject);
+	AZ(options & (~VRE_MASK_MATCH));
+	AN(groups);
+	AN(count);
+
+	if (length == 0)
+		length = PCRE2_ZERO_TERMINATED;
+	vre_limit(code, lim);
+	i = vre_capture(code, subject, length, 0, options,
+	    groups, &count, NULL);
+
+	if (i <= 0)
+		return (i);
+	return (count);
+}
+
 int
 VRE_sub(const vre_t *code, const char *subject, const char *replacement,
     struct vsb *vsb, const volatile struct vre_limits *lim, int all)

lib/libvarnishapi/generate.py

@@ -192,6 +192,7 @@ fo.write("""
 #include <ctype.h>
 #include <stdio.h>
 
+#include "vdef.h"
 #include "vqueue.h"
 #include "vre.h"