fix copying elements with non-latin content like comment element, or
variables with description in non-latin character set

before any non-latin text was converted after copying to strings like 'Это...'

fix issue that if functional block is dragged from project panel into
ST text editor and in dialog 'Please enter a block name' button
'cancel' is pressed, despite of cancel text about drag'n'dropped type
is pasted in ST program.

fix regression introduced by changeset: 1431:28e9d479aa65 [Use '-p' command line option when running matiec (iec2c)]

Variable matiec_flags in c_ext.py and PythonFileCTNMixin.py is not
used for flags for matiec (IEC to C compiler) actually, but it's used
to compile C-code generated for extensions using normal C-compiler,
like gcc.