The following warning is removed:
Visual Studio 14.0
1. warning C4275: non dll-interface class 'std::exception' used as
   base for dll-interface class 'vtkpugixml::xpath_exception'

This change replaces xpath_node_set single element storage with a
single-element array in hopes that this would silence Coverity false
positive about getting a singleton pointer.

Additionally, it refactors _assign member to unify small and large
buffer codepaths since they are basically identical.

Fixes #233 (hopefully)

Fixes #224.

Define noexcept using _MSC_VER instead of _MSC_FULL_VER (first release
of MSVC 2015 should have it), remove redundant PUGIXML_HAS_NOEXCEPT and
define PUGIXML_NOEXCEPT_IF_NOT_COMPACT in terms of PUGIXML_NOEXCEPT.

* Adds noexcept specifiers to the move special members of xml_document, but only #ifndef PUGIXML_COMPACT

* Adds a macro definition to be able to use noexcept with supporting compilers

* Adds noexcept specifier to move special members of xpath_node_set, xpath_variable_set and xpath_query, but not of xml_document as it has a throwing implementation

Enables usage of override specifier for MSVC compilers (beginning with 17.0 which is the compiler of Visual Studio 2012)

This change implements the initial version of move construction and
assignment support for documents.

When moving a document to another document, we always make sure move
target is in "clean" state (empty document), and proceed by relocating
all structures in the most efficient way possible.

Complications arise from the fact that the root (document) node is
embedded into xml_document object, so all pointers to it have to change;
this includes parent pointers of all first-level children as well as
allocator pointers in all memory pages and previous pointer in the first
on-heap memory page.

Additionally, compact mode makes everything even more complicated
because some of the pointers we need to update are stored in the hash
table (in fact, document first_child pointer is very likely to be there;
some parent pointers in first-level children will be using
compact_shared_parent but some won't be) which requires allocating a new
hash table which can fail.

Some details of this process are not fully fleshed out, especially for
compact mode; and this definitely requires many tests.

These functions were deprecated via comments in 1.5 but never got the
deprecated attribute; now is the time!

Using deprecated functions produces a warning; to silence it, this
change moves the relevant tests to a separate translation unit that has
deprecation disabled.

Setting this flag outputs start and end tag for every element, including empty
elements.

Fixes #118.

MSVC 2010 supported move semantics (partially - but should be good enough for
our use case).

Do it in one place and set PUGIXML_HAS_MOVE if it's available.

VS 2013 supports C++11, but __cplusplus macro isn't updated, and it is 199711 so the old check always fails, even though the compiler supports c++11.

This makes the coverage for basic numeric types complete (sans long double).

Fixes #78.

Git warns when it finds "whitespace errors". This commit gets
rid of these whitespace errors for code and adoc files.

Since round-tripping should not be a problem any more don't mention it.

When this flag is true, PCDATA value is saved to the parent element instead of
allocating a new node.

This prevents some documents from round-tripping since it loses information,
but can provide a significant memory reduction and parsing speedup for some
documents.

This does not really matter too much but it's better to be consistent.

Extra argument 'hint' is used to start the attribute lookup; if the attribute
is not found the lookup is restarted from the beginning of the attriubte list.

This allows to optimize attribute lookups if you need to get many attributes
from the node and can make assumptions about the likely ordering. The code is
correct regardless of the order, but it is faster than using vanilla lookups
if the order matches the calling order.

Fixes #30.

xpath_query, xpath_node_set and xpath_variable_set are now moveable.

This is a nice performance optimization for variable/node sets, and enables
storing xpath_query in containers without using pointers (it's only possible
now since the query is not copyable).

xpath_variable_set is essentially an associative container; it's about time it
became copyable.

Implementation is slightly tricky due to out of memory handling. Both copy ctor
and assignment operator have strong exception guarantee (even if exceptions are
disabled! which translates to "roll back on allocation errors").

The type of the variable is now initialized correctly in the ctor, so that there
is no interim invalid state.

Since the type of the set was updated before assignment, assigning in
out-of-memory condition could change the type to not match the content.

Fix code style and revert redundant parameters/whitespace changes.

Also remove format_each_attribute_on_new_line - we're only introducing one
extra formatting flag. The flag implies format_indent but does not include its
bitmask.

Also add a few more tests.

Fixes #14.

Also fix the float/double member order in the header file.