Fix two constants which were broken when the code was converted to UTF-8.
SynMain.h: add two missing constants, MONO and SEREO.
SynSon.h: add and use TEMPS_SECU_ECR and TEMPS_SECU_LEC.
Synthe.h: add missing _stdcall.
Improve sound card handling.
synGlobal.cpp: get rid of useless comment at end of file.
SynParle.cpp: file update.
SynTex.cpp: minor comments fixup.
Synthe.cpp: several fixes and improvements.
SynTrans.cpp: replace itoa with sprintf to make code more portable.
Get rid of useless file SynIConv.cpp.
SynSon.cpp: fix case in header names.