http: fix the broken >3 digit response code detection

When the "reason phrase" in the HTTP status line starts with a digit,
that was treated as the forth response code digit and curl would claim
the response to be non-compliant.

Added test 1466 to verify this case.

Regression brought by 5dc594e44f
Reported-by: Glenn de boer
Fixes #7738
Closes #7739

lib/http.c

@@ -4232,9 +4232,9 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
         char separator;
         char twoorthree[2];
         int httpversion = 0;
-        int digit4 = -1; /* should remain untouched to be good */
+        char digit4 = 0;
         nc = sscanf(HEADER1,
-                    " HTTP/%1d.%1d%c%3d%1d",
+                    " HTTP/%1d.%1d%c%3d%c",
                     &httpversion_major,
                     &httpversion,
                     &separator,
@@ -4250,13 +4250,13 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
 
         /* There can only be a 4th response code digit stored in 'digit4' if
            all the other fields were parsed and stored first, so nc is 5 when
-           digit4 is not -1 */
-        else if(digit4 != -1) {
+           digit4 a digit */
+        else if(ISDIGIT(digit4)) {
           failf(data, "Unsupported response code in HTTP response");
           return CURLE_UNSUPPORTED_PROTOCOL;
         }
 
-        if((nc == 4) && (' ' == separator)) {
+        if((nc >= 4) && (' ' == separator)) {
           httpversion += 10 * httpversion_major;
           switch(httpversion) {
           case 10:

tests/data/Makefile.inc

@@ -182,7 +182,7 @@ test1432 test1433 test1434 test1435 test1436 test1437 test1438 test1439 \
 test1440 test1441 test1442 test1443 test1444 test1445 test1446 test1447 \
 test1448 test1449 test1450 test1451 test1452 test1453 test1454 test1455 \
 test1456 test1457 test1458 test1459 test1460 test1461 test1462 test1463 \
-test1464 test1465 \
+test1464 test1465 test1466 \
 \
 test1500 test1501 test1502 test1503 test1504 test1505 test1506 test1507 \
 test1508 test1509 test1510 test1511 test1512 test1513 test1514 test1515 \

tests/data/test1466

@@ -0,0 +1,45 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+</keywords>
+</info>
+
+<reply>
+<data>
+HTTP/1.1 405 405
+Content-Length: 6
+Connection: close
+
+-foo-
+</data>
+</reply>
+
+#
+# Client-side
+<client>
+<server>
+http
+</server>
+
+<name>
+HTTP GET with 3-digit response and only digits in reason
+ </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
+User-Agent: curl/%VERSION
+Accept: */*
+
+</protocol>
+</verify>
+</testcase>