adapt the Windows build files accordingly.


VC++Files/tests/mysql_client_test.dsp:
  As the directory structure on Windows now resembles that on Unix (no more
  "tests/tests", by the correction in "make_win_src_distribution.sh"), the location
  of "mysql_client_test.*" has changed. Adapt the build tools accordingly.
VC++Files/tests/mysql_client_test_ia64.dsp:
  As the directory structure on Windows now resembles that on Unix (no more
  "tests/tests", by the correction in "make_win_src_distribution.sh"), the location
  of "mysql_client_test.*" has changed. Adapt the build tools accordingly.
scripts/make_win_src_distribution.sh:
  1) The semantics of "cp -R src targ" depend on the (non)existence of "targ".
  By simply doing "$CP -R $i $BASE/$i", the directory hierarchy below $BASE differed
  from the source for each "$i" that already existed as a target directory.
  This is now prevented by checking the existence and adapting the command.
  
  2) Comment where "$BASE" (the target directory) comes into existence.
  
  3) Introduce an "abort" function as a start point for more sanity checks, use it.