[thread.lock.algorithm] Use code font for try_lock().
[ios.overview] Remove stray space
[stringstream.cons], [stringstream.members] Replace rSec2 with rSec3.
[ostreambuf.iter.cons] Null pointer is not a verb.

Combine adjacent paragraphs into one itemdescr.

Fixes #384.
[expr.const] Fix typo 'evalution'.
[stmt.for] Remove misplaced hyphen in "declarative region".
[stmt.for] Dehyphenate for-statement; there is no such grammar term.
[dcl.enum] Use more natural and unambiguous phrasing around the
definition of whether an enumeration type's underlying type is fixed.
[temp] Add L suffix to literal value example definition of constexpr
variable template 'pi', to address questions about whether it would
do the right thing for 'long double'.
[over.literal] Use a valid parameter-declaration-clause for a literal
operator in example that claims to be "OK".
Update configuration for building N4140.
Update configuration for building drafts after N4140.
Add papers N4138, N4139, N4140: New working draft and editor's reports.