[lib] Adjust \indexlibrarymember{class}{member} to \indexlibrarymembe…

[YexuanXiao]

…r{member}{class}

According to the Style Guidelines, the \indexlibrarymember command should take the member name as its first parameter and the class name as the second. After reviewing all existing \indexlibrarymember calls, I found the following classes violate this rule (some even use different orders within the same class):

• array
• span
• locale
• ctype
• codecvt
• num_get
• num_put
• numpunct
• collate
• time_get
• money_get
• money_put
• moneypunct
• messages
• regex_traits
• basic_regex
• sub_match
• match_results
• regex_token_iterator
• thread

(note: "span" is also used as a member name in iostreams.tex, but the iostreams.tex file does not contain such issues).

[eisenwave]

The same inconsistency surprised me as well. However, the \indexlibrarymember macro is commutative anyway:

\newcommand{\indexlibrarymember}[2]{\indexlibraryboth{\idxcode{#1}}{\idxcode{#2}}}

... so this issue doesn't have any visible impact to the reader, even though the markup inconsistency is surprising.

[YexuanXiao]

... so this issue doesn't have any visible impact to the reader, even though the markup inconsistency is surprising.

I noticed this issue while trying to add missing member indexes (which I plan to proceed with after this PR is merged). The inconsistency was confusing, so it would be best to correct it according to the Guidelines.