lv_txt_get_next_word() function

Get the next word of text. A word is delimited by break characters. If the word cannot fit in the max_width space, obey LV_TXT_LINE_BREAK_LONG_* rules. If the next word cannot fit anything, return 0. If the first character is a break character, returns the next index. Example calls from lv_txt_get_next_line() assuming sufficient max_width and txt = "Test text\n" 0123456789 Calls would be as follows: 1. Return i=4, pointing at breakchar ' ', for the string "Test" 2. Return i=5, since i=4 was a breakchar. 3. Return i=9, pointing at breakchar '\n' 4. Parenting lv_txt_get_next_line() would detect subsequent '\0' TODO: Returned word_w_ptr may overestimate the returned word's width when max_width is reached. In current usage, this has no impact.