make.bat: change current directory

First thing after calling make.bat: switch current directory to folder make.bat resides in.
Purpose: easy external call of make.bat.
/J.
make.bat: change current directory

amendment for switching between drives and flipping back to initial cur dir at end of make.bat
Update latexgen.cpp

added reset of var Dir_Old at the end.
Merge pull request #174 from jannick0/patch-1

make.bat: change current directory