Expose caf_init and caf_finalize in module to allow use with f2py, see #204

[zbeekman]

Fixes #204

At configure time, choose whether to expose the caf_init and
caf_finalize functions in the opencoarrays (extension) module by using -DCAF_EXPOSE_INIT_FINALIZE.

N.B. the semantics of using C pointers with Fortran still mystifies me a bit, and I don't really understand what the point of passing argc and argv to MPI_init is (since I always use fortran, where the only arg is ierr). So for my interface to caf_init which takes argc and argv as arguments, I have declared both as type(c_ptr) so it is the users responsibility to pass the appropriate c_ptr in to them. In my testing I just passed c_null_ptrs and it seemed to work fine. Also, please note, that the caf compiler wrapper script does not pass in the installed module file for open coarrays aware (OCA) compilers (GCC/GFortran) to the compiler, so you'll have to add something like -J/usr/local/mod or whatever to the caf script if you use it and want the compiler to find your installed module file and compile time.

@amckinstry: will this suit your needs? Please take a look and let me know if you need any changes.

[codecov-io]

Current coverage is 48.18% (diff: 100%)

Merging #251 into master will not change coverage

@@             master       #251   diff @@
==========================================
  Files             2          2          
  Lines           907        907          
  Methods          42         42          
  Messages          0          0          
  Branches        195        195          
==========================================
  Hits            437        437          
  Misses          392        392          
  Partials         78         78          

Powered by Codecov. Last update 13a6255...37900d4

[zbeekman]

LGTM