fix escape bug

让sql保持原样

src/main/java/com/alibaba/druid/sql/dialect/postgresql/parser/PGLexer.java

@@ -92,6 +92,7 @@ public class PGLexer extends Lexer {
                     hasSpecial = true;
                 }
 
+                putChar('\\');
                 switch (ch) {
                     case '\0':
                         putChar('\0');
@@ -137,6 +138,7 @@ public class PGLexer extends Lexer {
                     arraycopy(mark + 1, buf, 0, bufPos);
                     hasSpecial = true;
                     putChar('\'');
+                    putChar('\'');
                     continue;
                 }
             }