Fix most of bug #16051 with redisplay loops when resizing tool-bar.
src/xdisp.c (tool_bar_height): Use WINDOW_PIXEL_WIDTH to set up the iterator X limits, not FRAME_TOTAL_COLS, for consistency with what redisplay_tool_bar does. Improve and fix commentary. (hscroll_window_tree): Don't assume w->cursor.vpos is within the limits of the glyph matrices.
Showing with 34 additions and 13 deletions