Inline Length(DynamicArray)

Up until now a helperfunction was called at runtime. This change inlines
the whole code in the same way Length(AnsiString) works. As dynamic
arrays do not record their length but their highest index, an additional
"OP_ADD" is this case.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25227 3ad0048d-3df7-0310-abae-a5850022a9f2