Overflow protection of the response buffer

When receiveing data and the remote sends more data than what we expect,
the response buffer could be overrun and corrupt the stack.

Send the maximum buffer length to lowLevelWriteRead(),
which declares a local buffer[PMAC_MAXBUF_] where data is received.
When the response is longer than expected, it is clipped and a warning
written.
Improve the connect

connectIt() is not thread safe:
  The function connectIt() is called at 2 different places,
  which run in different threads in the EPICS framwork.
  But connectIt() is not thread safe, a semaphore is missing,
  when thread A calls connectIt() and in the middle of the operation
  thread B calls connectIt() again.
  Instead of adding a semaphore to make sure that the function can complete
  the work before being executed one more time we simply remove one caller.

connectSSH(): Improve the start of the shell
  After connection via ssh to the machine, a shell is started.
  The shell will print a "welcome", which can be more than one line.
  We need to make sure that all the welcome line(s) are read,
  before sending the gpascii command.
  Depending on the speed of the connection, the CPU load on the controller,
  the network load and the configured prompt, contents of e.g. ~/bashrc ...
  this can be difficult to do reliable.
  And the IOC may be out of sync, issuing the gpascii command too early,
  or wrongly treating welcome lines as a response from the gpascii command.

  Avoid this mis-synchonization:
  Introduce a dialog with the shell; set different prompts and read them back,
  to make sure that really all welcome lines had been read and the shell is
  ready to accept the gpascii command.

Debug:
  printf() does not work really well for control chars like '\r' or
  ASCII ACK ('\006' in octal).
  Add a compiler filag DEBUG_CTRL_CHARS to sshDriver.cpp to be able
  to print these control characters as '\r', '\n' or '\006'
Merge pull request #3 from tboegi/140901_1034_overflow_protection_one_connect

140901 1034 overflow protection one connect