Use emplace() for associative containers.

* HACKING: Adjust requirements.  g++4.8 is now OK
for all our targets.
* iface/dve2/dve2.cc, src/dstarparse/dstarparse.yy
src/dstarparse/nsa2tgba.cc, src/graph/ngraph.hh,
src/ltlast/atomic_prop.cc, src/ltlast/binop.cc, src/ltlast/bunop.cc,
src/ltlast/multop.cc, src/ltlast/unop.cc, src/ltlvisit/mark.cc,
src/ltlvisit/relabel.cc, src/taalgos/emptinessta.cc,
src/taalgos/tgba2ta.cc, src/tgba/tgbaexplicit.hh, src/tgba/tgbagraph.hh,
src/tgba/tgbasafracomplement.cc, src/tgba/tgbatba.cc,
src/tgbaalgos/cycles.cc, src/tgbaalgos/degen.cc,
src/tgbaalgos/dtbasat.cc, src/tgbaalgos/dtgbasat.cc,
src/tgbaalgos/emptiness.cc, src/tgbaalgos/gtec/gtec.cc,
src/tgbaalgos/ltl2tgba_fm.cc, src/tgbaalgos/magic.cc,
src/tgbaalgos/ndfs_result.hxx, src/tgbaalgos/reachiter.cc,
src/tgbaalgos/scc.cc, src/tgbaalgos/sccfilter.cc, src/tgbaalgos/se05.cc,
src/tgbaalgos/simulation.cc, src/tgbaalgos/tau03.cc,
src/tgbaalgos/tau03opt.cc, src/tgbaalgos/weight.cc: Use emplace()
instead of insert(make_pair(...)) or insert(...::value_type(...)).

HACKING

@@ -229,25 +229,12 @@ C++11
 -----
 
   Spot uses some C++11 features, and therefore requires a C++11
-  compiler.  However (1) fully C++11-compliant compilers are
-  not yet well deployed, and (2) development tools have yet
-  to be updated to provide suitable C++11 support.  For instance
-  Swig 2.0, which we use for the Python bindings, does not
-  understand C++11.  The upcoming release of Swig 3 has better
-  support for C++11, we should switch to it as soon as possible.
+  compiler.  The code relies on features that are not available in
+  version of g++ older than 4.8, so this is our minimum requirement
+  for now.  Avoid features that require 4.9.
 
-  In the meantime, try to keep the C++11-specific syntax in the *.cc
-  files as much as possible.
-
-  Use only C++11 features that are available in clang 3.1 and g++ 4.6:
-   - http://gcc.gnu.org/projects/cxx0x.html
-   - http://clang.llvm.org/cxx_status.html
-
-  Library interfaces that should not be used:
-   - emplace() is not implemented for associative containers
-     (std::map, std::set, and their unordered ffriends) is
-     before g++ 4.8.  Use
-       x.insert(std::make_pair(...)) instead of x.emplace(...)
+  Reasonably recent versions of clang should work as well.  Our
+  build farm has clang++ 3.5.
 
 Encoding
 --------