Fix strbuf for gcc 4.8.2

Author: mrks

src/parser/flex_lexer.cpp

@@ -3193,7 +3193,7 @@ YY_RULE_SETUP
 case 154:
 YY_RULE_SETUP
 #line 249 "flex_lexer.l"
-{ BEGIN singlequotedstring; strbuf = std::stringstream{}; }
+{ BEGIN singlequotedstring; strbuf.clear(); strbuf.str(""); }  // Clear strbuf manually, see #170
 	YY_BREAK
 case 155:
 YY_RULE_SETUP

src/parser/flex_lexer.l

@@ -246,7 +246,7 @@ COMMIT      TOKEN(COMMIT)
 	return SQL_IDENTIFIER;
 }
 
-\'                          { BEGIN singlequotedstring; strbuf = std::stringstream{}; }
+\'                          { BEGIN singlequotedstring; strbuf.clear(); strbuf.str(""); }  // Clear strbuf manually, see #170
 <singlequotedstring>\'\'    { strbuf << '\''; }
 <singlequotedstring>[^']*   { strbuf << yytext; }
 <singlequotedstring>\'      { BEGIN 0; yylval->sval = strdup(strbuf.str().c_str()); return SQL_STRING; }