(CMAKE ROSE) define Flex symbols on Windows

This resolves linker errors that were caused by the lack of a
Flex library on Windows.
(CMAKE ROSE) resolve C2036

This commit resolves the following compilation error:
error C2036: 'void *' : unknown size

This change still needs to be tested to ensure that it does not
modify the behavior of this code.
(CMAKE ROSE) mmap workaround for Windows

Define dummy mmap functions when building with Visual Studio.
(CMAKE ROSE) workaround lack of pthreads

Only use pthread-specific code when it is available.
(CMAKE ROSE) resolve linker error

This commit resolves the following linker error:
error LNK2001: unresolved external symbol
  "long __cdecl rose_getline(char * *,unsigned int *,struct _iobuf *)"
referenced from CompilerOutputReader.obj