...including those that have no corresponding textual IANA character set name
representation, like RTL_TEXTENCODING_MS_950 which is apparently used in some
DBase files.

In the past, if eCharSet was RTL_TEXTENCODING_DONTKNOW in lcl_getDBaseConnection
it was sent as an empty string CharSet property, which the receiving
OConnection::construct translated back to

  else
      m_nTextEncoding = RTL_TEXTENCODING_DONTKNOW;

so the net effect remains the same for that special case.

Change-Id: I84eec8a93d000752b3c429976c58721ea9ea32a4
Reviewed-on: https://gerrit.libreoffice.org/50772Reviewed-by: Lionel Elie Mamane <lionel@mamane.lu>
Tested-by: Jenkins <ci@libreoffice.org>