tests/wkt_test:

Added some negative number cases to point tests.
wkt:

Added negative coordinate support to point wkt loading.

This was a bug.
tests/wkt_test:

Added some negative values to the tests for point wkt loading.
wkt:

Simplified an import.
tests/wkt_test:

Added some negative values to test_dumps_linestring_2d.
tests/wkt_test:

Added negative test values to test_loads_linestring_2d.
wkt:

Added handling for negative numbers to `__load_linestring`.