Previously there was no guarantee that the tests that check for out of memory
handling behavior are actually correct - e.g. that they correctly simulate out
of memory conditions.

Now every simulated out of memory condition has to be "guarded" using
CHECK_ALLOC_FAIL. It makes sure that every piece of code that is supposed to
cause out-of-memory does so, and that no other code runs out of memory
unnoticed.

When parsing XPath variables, we need to perform a heap allocation; if it
fails, an xpath_exception instead of bad_alloc used to be thrown.

Now we throw the exception of a correct type so that xpath_exception means
'parsing error'.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1077 99668b35-9821-0410-8761-19e4c4f06640

Also fix MSVC6 compilation (make convertions to function pointers explicit).

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1076 99668b35-9821-0410-8761-19e4c4f06640

More tests for out-of-memory and other edge conditions

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1075 99668b35-9821-0410-8761-19e4c4f06640

select_node is shorter and mistyping nodes as node or vice versa should
not lead to any issues since return types are substantially different.

select_single_node method still works and will be deprecated with an
attribute and removed at some point.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1065 99668b35-9821-0410-8761-19e4c4f06640

git-svn-id: http://pugixml.googlecode.com/svn/trunk@696 99668b35-9821-0410-8761-19e4c4f06640

git-svn-id: http://pugixml.googlecode.com/svn/trunk@692 99668b35-9821-0410-8761-19e4c4f06640

git-svn-id: http://pugixml.googlecode.com/svn/trunk@683 99668b35-9821-0410-8761-19e4c4f06640

git-svn-id: http://pugixml.googlecode.com/svn/trunk@681 99668b35-9821-0410-8761-19e4c4f06640

git-svn-id: http://pugixml.googlecode.com/svn/trunk@679 99668b35-9821-0410-8761-19e4c4f06640