Manpage update, other small changes

Changes:
* manpage updated
* add .gitignore; files generated by autoreconf in mp4v2 are now ignored
* removed "mp4v2/include/mp4v2/project.h" since it's automatically created by configure script
* add Linux build script as replacement for BUILD_Linux.txt
* minor changes in Debian folder
* main.cpp: now displays the version of the used mp4v2 lib
* source files moved to src/