tests/Makefile: always stop server before rebuild
Implement URI path splitting

.gitmodules:
    Use sebgod/mongoose fork

Make.options:
    Define -DMONGOOSE_NO_URL_DECODE

src/Makefile:
    Conform to flag name change (CFLAGS -> MONGOOSE_CFLAGS).

src/Mercury.options:
    Remove unneeded options.

src/mercury_mongoose.m:
    Include path util module.

src/mongoose:
    Implement MONGOOSE_NO_URL_DECODE flag.

src/path_util.m:
    split_path/1 for URI pathes.

tests/test_mercury_mongoose.m:
    Conform to the above changes.