curl_version_info: offer quic (and h3) library info

Closes #4216

docs/libcurl/curl_version_info.3

@@ -78,6 +78,15 @@ typedef struct {
                                   (MAJOR << 24) | (MINOR << 12) | PATCH */
   const char *brotli_version; /* human readable string. */
 
+  /* when 'age is CURLVERSION_SIXTH or alter (7.66.0 or later), these fields
+     also exist */
+  unsigned int nghttp2_ver_num; /* Numeric nghttp2 version
+                                   (MAJOR << 16) | (MINOR << 8) | PATCH */
+  const char *nghttp2_version; /* human readable string. */
+
+  char *quic_version;          /* human readable quic (+ HTTP/3) library +
+                                  version or NULL */
+
 } curl_version_info_data;
 .fi
 

include/curl/curl.h

@@ -2762,7 +2762,8 @@ typedef struct {
   unsigned int nghttp2_ver_num; /* Numeric nghttp2 version
                                    (MAJOR << 16) | (MINOR << 8) | PATCH */
   const char *nghttp2_version; /* human readable string. */
-
+  char *quic_version;          /* human readable quic (+ HTTP/3) library +
+                                  version or NULL */
 } curl_version_info_data;
 
 #define CURL_VERSION_IPV6         (1<<0)  /* IPv6-enabled */

lib/version.c

@@ -395,7 +395,8 @@ static curl_version_info_data version_info = {
   0,    /* brotli_ver_num */
   NULL, /* brotli version */
   0,    /* nghttp2 version number */
-  NULL  /* nghttp2 version string */
+  NULL, /* nghttp2 version string */
+  NULL  /* quic library string */
 };
 
 curl_version_info_data *curl_version_info(CURLversion stamp)
@@ -479,6 +480,14 @@ curl_version_info_data *curl_version_info(CURLversion stamp)
   }
 #endif
 
+#ifdef ENABLE_QUIC
+  {
+    static char quicbuffer[80];
+    Curl_quic_ver(quicbuffer, sizeof(quicbuffer));
+    version_info.quic_version = quicbuffer;
+  }
+#endif
+
   (void)stamp; /* avoid compiler warnings, we don't use this */
 
   initialized = true;