#24 WhiteSpaceCondense=false fixes

[Hauke Duden]

This patch fixes two issues when WhiteSpaceCondense is
set to false.

1) TiXmlDocument::Parse used to enter an infinite loop
sometimes (depending on xml text) because
pWithWhiteSpace was not updated correctly in ReadValue.
More precisely, pWithWhiteSpace was not updated after
opening tags were parsed, so when the next text node
was found the same tags were parsed over and over again.

2) Whitespace-only text between tags used to be skipped
altogether, even though WhiteSpaceCondense was set to
false.

Both issues are fixed with this patch. It has been
created against the last release version (2.3.4).

[Hauke Duden]