xmllint --pretty crashed without following numeric argument

https://bugzilla.gnome.org/show_bug.cgi?id=674789

We need to check for NULL argument before calling atoi()
Fix potential NULL pointer dereferences in regexp code

https://bugzilla.gnome.org/show_bug.cgi?id=707749

Fix 3 cases where we might dereference NULL
Fix a potential NULL dereference in tree code

https://bugzilla.gnome.org/show_bug.cgi?id=707750

Also reported by Gaurav, simple fix to check the pointer before
dereference
Fix pointer dereferenced before null check

for https://bugzilla.gnome.org/show_bug.cgi?id=708364

xmlValidateElementContent is a private function but should still
check the ctxt argument before dereferencing
run close socket on Solaris, same as we do on other platforms

https://bugzilla.gnome.org/show_bug.cgi?id=705188
Drop not needed checks

https://bugzilla.gnome.org/show_bug.cgi?id=704075
Avoid a deadcode in catalog.c

For https://bugzilla.gnome.org/show_bug.cgi?id=703504
Avoid some dead code and cleanup in relaxng.c

https://bugzilla.gnome.org/show_bug.cgi?id=705388

Code needed a bit of cleanup
fix some tabs mixing incompatible with python3

Patrick Welche <prlw1@cam.ac.uk> raised this issue