Readme for distribution of ltl2dstar with storm:

Differences to the common version:
- A small fix in in DRA.h, which allows the compilation with new compilers
- Changed makefile: Storm directly uses the code of ltl2dstar (i.e. without calling the binary), so the makefile was changed in the following way:
  - The target "lib" creates a static library (libltl2dstar.a) which does not contain the source code of the main source file (ltl2dstar_main.cpp).
  - The target "all" creates this static library and an executable file (ltl2dstar), using the main source file.