Fix std.traits for large input

std.traits: EnumMembers, isExpressionTuple, isTypeTuple & Largest balks
at large input
EnumMembers now works with single-member enums.
Merge branch 'master' of https://github.com/D-Programming-Language/phobos
fix Issue 10230 - Duplicated buttons for runnable examples
Merge remote-tracking branch 'upstream/master'
Solve conflicting "chunks" declaration
make ChunksImpl private
It appears that whoever changed the name of the range parameter to encode didn't rename the parameter everywhere in the function.
Fix emplace
Fix spelling
Issue 9559 - Range of Nullable doesn't work with std.array.array
Tweak emplace some
emplace: diagn for quals; simplf alias this brnch
make "emplace(singleArg)" safe pure nothrow
reword emplace deprecation message
Yet another emplace unittest that is fixed
lookbehind for ctRegex
Partial fix for Issues 7067 and 10434 - std.random.RandomCover

The existing RandomCover design is fatally flawed because it
requires a RNG as input, which it then copies internally by
value.  So, unless the user is smart enough to pass something
like e.g. SomeRNG(unpredictableSeed), there will be unintended
correlations in random behaviour.

This partial fix follows the design of RandomSample in allowing
RandomCover to use the thread-global default RNG rndGen.  It
also improves the choice of template parameter and variable
names in line with Issue 10434.
Partial fix for Issue 10434 - std.random.RandomSample

In line with changes to RandomCover, this patch tweaks
the choice of template parameter and variable names in
order to bring clarity and uniformity to the module.
Correct the .save methods for RandomCover and RandomSample.

RandomCover and RandomSample should only be save'able if:

   * the input is a forward range

   * the thread-global RNG rndGen is not being used

   * the RNG being used is a forward range.