Show symbols whose documentation contains matches for PATTERN.
PATTERN can be a word, a list of words (separated by spaces),
or a regexp (using some regexp special characters). If it is a word,
search for matches for that word as a substring. If it is a list of words,
search for matches for any two (or more) of those words.
Note that by default this command only searches in the file specified by
`internal-doc-file-name'; i.e., the etc/DOC file. With C-u prefix,
or if `apropos-do-all' is non-nil, it searches all currently defined
Returns list of symbols and documentation found.