[text] move_word_backward/forward fixes
[text] move_word_backward/forward fixes

clutter_text_move_word_backward/forward() calls did not use the
start argument consistently. Also, clutter_text_move_word_forward()
bound check checked the wrong end.

Fixes #1765

Backport from master:

  8c00d705c0ec009c08950f314ab896b6ff40aa37

Signed-off-by: Emmanuele Bassi <049ee2061f71220e5aaf33f5be422fc2a2b06a44@linux.intel.com>

tardyp/clutter,tardyp/clutter,tardyp/clutter