http: write last header line late

- HEADERFUNCTIONS might inspect response properties like
  CURLINFO_CONTENT_LENGTH_DOWNLOAD_T on seeing the last header line. If
  the line is being written before this is initialized, values are not
  available.

- write the last header line late when analyzing a HTTP response so that
  all information is available at the time of the writing.

- add test1485 to verify that CURLINFO_CONTENT_LENGTH_DOWNLOAD_T works
  on seeing the last header.

Fixes #13752
Reported-by: Harry Sintonen
Closes #13757

tests/data/Makefile.inc

@@ -188,7 +188,7 @@ test1447 test1448 test1449 test1450 test1451 test1452 test1453 test1454 \
 test1455 test1456 test1457 test1458 test1459 test1460 test1461 test1462 \
 test1463 test1464 test1465 test1466 test1467 test1468 test1469 test1470 \
 test1471 test1472 test1473 test1474 test1475 test1476 test1477 test1478 \
-test1479 test1480 test1481 test1482 test1483 test1484 \
+test1479 test1480 test1481 test1482 test1483 test1484 test1485 \
 \
 test1500 test1501 test1502 test1503 test1504 test1505 test1506 test1507 \
 test1508 test1509 test1510 test1511 test1512 test1513 test1514 test1515 \

tests/data/test1485

@@ -0,0 +1,51 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+</keywords>
+</info>
+
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK
+Server: Someone
+Content-Length: 7
+
+123456
+</data>
+<datacheck>
+HTTP/1.1 200 OK
+Server: Someone
+Content-Length: 7
+
+123456
+</datacheck>
+</reply>
+# Client-side
+<client>
+<server>
+http
+</server>
+<tool>
+lib%TESTNUMBER
+</tool>
+<name>
+get curlinfo on last header in callback
+</name>
+<command>
+http://%HOSTIP:%HTTPPORT/%TESTNUMBER
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+GET /%TESTNUMBER HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>