new prepare_win32.sh script

Hi,
  I committed a new script in misc directory, prepare_win32.sh. I use
this script to cross compile FreeTDS for windows (either win32 and
win64). I just added support to compile dblib unittests against MS
dblib library (ntwdblib.dll). Perhaps it contains some path or
reference to my directories and configurations, for instance you need
sqldb.h and sqlfront.h in $HOME/cpp/freetds/dblib (use MS headers!!).
I just compiled and tried to test but:
- I miss to include *.sql files from src/dblib/unitests. commit waiting
- I don't know how to configure a server using MS dblib... ODBC have
an applet in control panel, but dblib... ?? ok, I found, use "Client
Network Utility" setting aliases.

Well... MS dblib is very stable.. many test core... probably FreeTDS
do more argument checking.

freddy77