Adding some missing NULL checks

in SAX2 DOM building code and in the HTML parser
xmlSaveUri() incorrectly recomposes URIs with rootless paths

For https://bugzilla.gnome.org/show_bug.cgi?id=731063

xmlSaveUri() of libxml2 (snapshot 2014-05-31 and earlier) returns
bogus values when called with URIs that have rootless paths
(e.g. "urx:b:b" becomes "urx://b%3Ab" where "urx:b%3Ab" would be
correct)
Fix a link to James SAX documentation old page
Adding a check in case of allocation error

For https://bugzilla.gnome.org/show_bug.cgi?id=733043

There is missing Null condition in xmlRelaxNGValidateInterleave of
relaxng.c
Dereferencing it may cause a crash.
Add a missing argument check

For https://bugzilla.gnome.org/show_bug.cgi?id=733042

the states argument of xmlRelaxNGAddStates() ought to be checked too
Add a couple of misisng check in xmlRelaxNGCleanupTree

For https://bugzilla.gnome.org/show_bug.cgi?id=733041

check cur->parent before dereferencing the pointer even if
a null parent there should not happen
Also fix a typo
Fix a potential NULL dereference

For https://bugzilla.gnome.org/show_bug.cgi?id=733040

xmlDictLookup() may return NULL in case of allocation error,
though very unlikely it need to be checked.
Fix various Missing Null checks

For https://bugzilla.gnome.org/show_bug.cgi?id=732823
XMl Shell command "cd" does not handle "/" at end of path

For https://bugzilla.gnome.org/show_bug.cgi?id=731832
small fix
Merge branch 'master' of git://git.gnome.org/libxml2 into os400