[atomics.types.operations.req] Hyphenate "non member".

Change "their corresponding explicit" to "their corresponding explicit
functions".
SFINAE is a Remark not Requires.
Merge pull request #311 from lichray/no-sfinae-in-remark

[util.smartptr] SFINAE condition belongs in a Remark paragraph, not a Requires paragraph.
[expr.alignof] Use "is", not "shall be", to express a requirement on the
implementation rather than one on the program.
Merge pull request #299 from jwakely/atomic-explicit

[atomics.types.operations.req] Hyphenate "non member" and add missing word "functions".
[basic.lval] Correct example of xvalue to not suggest that a function call
returning an rvalue reference to a function type is an xvalue.

Fixes #315
[expr.const] Add missing 'const' to examples invalidated by N3598.

Fixes CWG1683.
[class.mem] Format definition of 'layout-compatible' as a definition,
add it to the index, and unify spelling of this index entry across the
three places where it is defined.
Add 1ex of vertical space between numbered paragraphs.
[dcl.dcl] Split the introduction of *declaration*, *simple-declaration*, and
*attribute-declaration* into three separate paragraphs, rather than having a
single paragraph spanning a whole page.
Remove paper.
Remove unused definitions of terms 'formal argument', 'actual argument', and
'actual parameter'. Unify uses of 'formal parameter' and 'parameter' to all use
the vastly more common term 'parameter' and remove the definition of 'formal
parameter'.
Tighten the words we use in "Throughout this [sub]clause" wording
to introduce a set of requirements for template arguments based
on their names, and make these paragraphs consistent.
Fix vertical whitespace around grammar definitions and bullets.
Remove trailing blank lines at ends of grammar productions.
US-1 Add numbering for bullets. Bullets are numbered within the surrounding
paragraph or bullet, not within the relevant bulleted list, so that numbers are
unique. The main text formatting is unchanged; bullet numbers are placed in the
left margin, just like paragraph numbers.

Also fixes #177.
[memory.general] Add missing `<` character to C header name.
Parenthesize bullet numbers to make it more obvious that text after the bullets
is part of the preceding paragraph.
[class] Move paragraph breaks to improve vertical whitespace.
[ratio.syn] Use digit separators to make large numbers more readable.