HTTP parser: fixed parsing of target after literal space character.

In theory, all space characters in request target must be encoded; however,
some clients may violate the specification.  For the sake of interoperability,
Unit supports unencoded space characters.

Previously, if there was a space character before the extension or arguments
parts, those parts weren't recognized.  Also, quoted symbols and complex
target weren't detected after a space character.

src/test/nxt_http_parse_test.c

@@ -205,6 +205,19 @@ static nxt_http_parse_test_case_t  nxt_http_test_cases[] = {
             0, 0, 1
         }}
     },
+    {
+        nxt_string("GET /na %20me.ext?args HTTP/1.0\r\n\r\n"),
+        NXT_DONE,
+        &nxt_http_parse_test_request_line,
+        { .request_line = {
+            nxt_string("GET"),
+            nxt_string("/na %20me.ext?args"),
+            nxt_string("ext"),
+            nxt_string("args"),
+            "HTTP/1.0",
+            0, 1, 1
+        }}
+    },
     {
         nxt_string("GET / HTTP/1.0 HTTP/1.1\r\n\r\n"),
         NXT_DONE,
@@ -212,7 +225,7 @@ static nxt_http_parse_test_case_t  nxt_http_test_cases[] = {
         { .request_line = {
             nxt_string("GET"),
             nxt_string("/ HTTP/1.0"),
-            nxt_null_string,
+            nxt_string("0"),
             nxt_null_string,
             "HTTP/1.1",
             0, 0, 1