Merge pull request #585 from alexrp/move-crc32

Deprecate crc32 and move it into std.crc32 (with new interface).
Merge pull request #608 from jmdavis/xml

Added warnings of future deprecation to modules that will be replaced.
Added peek, read, write, and append to std.bitmanip.

These functions make it easier to manipulate buffers of ubytes which are
meant to be parsed or written to as sequences of larger integral types.
They assume that the buffers hold their data in big endian.
Made it possible to give endianness to peek, read, write, and append.
Added checks to verify indices.
fix Issue 8203

Change RegexMatch objects to follow proper COW semantics
reduce benchmark count

- the 10M benchmark test accounts for 50% (5s) of datetime's
  unittest runtime
speed up SysTime opCmp tests

- cache DateTime to SysTime conversions
- 3000ms => 60ms
unittest for bug 8203
Merge pull request #622 from dawgfoto/fasterDateTimeUT

faster std.datetime unit tests
Merge pull request #623 from blackwhale/nested-regex

fix Issue 8203 std.regex.match() generates "not enough preallocated memory" 
Updated changelog for fix to issue 8203.
Merge pull request #621 from jmdavis/bitmanip

Added peek, read, write, and append to std.bitmanip.
Updated changelog for additions to std.bitmanip.
Added to BitArray in std.bitmanip:
- const modifiers
- const versions of opApply
- toHash method
- return value for length setter.
Merge pull request #618 from jmdavis/8195

Fix for issue# 8195.
Updated changelog for issue# 8195.
New implementation of visit and tryVisit that allows visitor structs and classes as well as delegate functions to be passed as parameters.

tryVisit is a new function which doesn't statically ensures that all types are handled by the visiting
functions. A VariantException is thrown if the algebraic holds a value which isn't handled by
the visitors.

visit and tryVisit share a common private template function as backend which does all the magic. applyDelegate and
applyVisitor have practically been merged into one new function.
Replace `delete` with `destroy` in std.signals
Merge pull request #589 from kbroman/patch-1

Fix comment describing gammaIncompleteComplInverse in std/mathspecial.d