kdb+ plugin uses unsafe C++ code

[Flying]

Assigning the result of str.c_str() to a pointer to be used later is against the C++ standard and is not safe. For example:

DolphinDBPlugin/kdb/src/kdb.cpp

Line 61 in 30535a5

 char* host = const_cast<char*>(hostStr.c_str()); 

[Flying]

There is also potential memory leak upon initial qIPC call in kdb::loadTable:

DolphinDBPlugin/kdb/src/kdb.cpp

Line 95 in 6bbadf9

 K res = k(handle_, arg,(K)0); 

DolphinDBPlugin/kdb/src/kdb.cpp

Line 108 in 6bbadf9

 K loadRes = k(handle_, loadArg,(K)0); 

[Flying]

This is not exception-safe:

DolphinDBPlugin/kdb/src/kdb.cpp

Line 1307 in 6bbadf9

 Connection* cup = new Connection(hostStr, port, usrStr);