Fix HTTP split parse edge case:

fix #257

This fixes a problem when doing split parsing (header then body).
The problem arises when the first buffer passed to the header
parser contains exactly the full header and nothing more. The
symptom is that when parsing the body, the parse will erroneously
be considered complete.

include/beast/http/impl/basic_parser_v1.ipp

@@ -45,6 +45,7 @@ namespace http {
 template<bool isRequest, class Derived>
 basic_parser_v1<isRequest, Derived>::
 basic_parser_v1()
+    : flags_(0)
 {
     init();
 }
@@ -61,12 +62,12 @@ basic_parser_v1(basic_parser_v1<
     , content_length_(other.content_length_)
     , cb_(nullptr)
     , s_(other.s_)
-    , flags_(other.flags_)
     , fs_(other.fs_)
     , pos_(other.pos_)
     , http_major_(other.http_major_)
     , http_minor_(other.http_minor_)
     , status_code_(other.status_code_)
+    , flags_(other.flags_)
     , upgrade_(other.upgrade_)
 {
     BOOST_ASSERT(! other.cb_);
@@ -88,13 +89,14 @@ operator=(basic_parser_v1<
     content_length_ = other.content_length_;
     cb_ = nullptr;
     s_ = other.s_;
-    flags_ = other.flags_;
     fs_ = other.fs_;
     pos_ = other.pos_;
     http_major_ = other.http_major_;
     http_minor_ = other.http_minor_;
     status_code_ = other.status_code_;
+    flags_ = other.flags_;
     upgrade_ = other.upgrade_;
+    flags_ &= ~parse_flag::paused;
     return *this;
 }
 
@@ -966,6 +968,7 @@ write(boost::asio::const_buffer const& buffer, error_code& ec)
             case body_what::pause:
                 ++p;
                 s_ = s_body_pause;
+                flags_ |= parse_flag::paused;
                 return used();
             }
             s_ = s_headers_done;