split h/c file - and fix compile errors on non-c99 compilers

[hjanuschka]

not sure - if you want to take it - but i needed the c/h file seperation in a larger project.
(mainly coz of note: previous definition of 'progress_free' was here and so on)

also fixes a few non-c99 compiler warnings

[hjanuschka]

ohhh i see #2 maybe closed after merging his one?

[hjanuschka]

also add's travis and coverity integration - and fixes outstanding memory leaks
verified with coverity - and tested with

valgrind --leak-check=full ./test-progress

==17595== HEAP SUMMARY:
==17595==     in use at exit: 0 bytes in 0 blocks
==17595==   total heap usage: 180 allocs, 180 frees, 18,464 bytes allocated
==17595== 
==17595== All heap blocks were freed -- no leaks are possible