(blank-style, blank-chars, blank-hspace-regexp, blank-space-regexp,

(blank-style, blank-chars, blank-hspace-regexp, blank-space-regexp,
blank-tab-regexp, blank-trailing-regexp, blank-space-before-tab-regexp,
blank-global-modes, blank-mode, global-blank-mode): Doc fixes.
(blank, blank-space-face, blank-hspace-face, blank-tab-face, blank-newline-face,
blank-trailing-face, blank-line-face, blank-space-before-tab-face,
blank-display-mappings, blank-chars-value-list, blank-style-value-list,
blank-toggle-options, global-blank-toggle-options, blank-help-text,
blank-interactive-char, blank-turn-on, blank-turn-off, blank-color-on,
blank-color-off): Fix typos in docstrings.