[container.alloc.reqmts] Better xrefs for allocator-aware containers

There are now more allocator-aware containers in the standard
than when this subclause was first written, so ensure we have
call outs to all relevent subclauses.

The current wording for 'basic_stacktrace' also shows how
containers can properly call out the allocator-aware container
requirements, now that they have their own, titled subclause.

Author: AlisdairM

source/containers.tex

@@ -908,7 +908,8 @@
 \rSec3[container.alloc.reqmts]{Allocator-aware containers}
 
 \pnum
-All of the containers defined in \ref{containers} and in~\ref{basic.string} except \tcode{array}
+Except for \tcode{array}, all of the containers defined in \ref{containers},
+\ref{stacktrace.basic}, \ref{basic.string}, and \ref{re.results}
 meet the additional requirements of an \defnadj{allocator-aware}{container},
 as described below.
 

source/regex.tex

@@ -2135,8 +2135,8 @@
 \indextext{requirements!container}%
 \indextext{requirements!sequence}%
 The class template \tcode{match_results} meets the requirements of an
-allocator-aware container and of
-a sequence container\iref{container.alloc.reqmts,sequence.reqmts}
+allocator-aware container\iref{container.alloc.reqmts} and of
+a sequence container\iref{container.requirements.general,sequence.reqmts}
 except that only
 copy assignment,
 move assignment, and

source/strings.tex

@@ -2378,7 +2378,7 @@
 the character traits requirements\iref{char.traits}.
 \begin{note}
 Every specialization \tcode{basic_string<charT, traits, Allocator>} is
-an allocator-aware container,
+an allocator-aware container\iref{container.alloc.reqmts},
 but does not use the allocator's \tcode{construct} and \tcode{destroy}
 member functions\iref{container.requirements.pre}.
 The program is ill-formed if