Merge 2021-02 LWG Motion 3

Author: tkoeppe

source/threads.tex

@@ -32,8 +32,8 @@
 the template argument shall return a value that is convertible to \tcode{bool}.
 If a template parameter is named \tcode{Clock},
 the corresponding template argument shall be a type \tcode{C}
-for which \tcode{is_clock_v<C>} is \tcode{true};
-otherwise the program is ill-formed.
+that meets the \oldconcept{Clock} requirements\iref{time.clock.req};
+the program is ill-formed if \tcode{is_clock_v<C>} is \tcode{false}.
 
 \rSec2[thread.req.exception]{Exceptions}
 

source/time.tex

@@ -2212,11 +2212,6 @@
 }
 \end{codeblock}
 
-\pnum
-\tcode{Clock} shall either
-meet the \oldconcept{Clock} requirements\iref{time.clock.req}
-or be the type \tcode{local_t}.
-
 \pnum
 If \tcode{Duration} is not a specialization of \tcode{duration},
 the program is ill-formed.