Added more error states and removed global error_connection

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=41443
Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=42304

I have added more xcb connection error states at xcb.h header.
Also I have removed global error_connection variable, and added
an interface that returns connection error state.

TBD:
I will segregate errors states in a separate header file and try to
provide more precise error states, in future. Also I will give patch
for libX11, in that patch xcb_connection_t::has_error will be passed
to default io handler of libX11. This value can then be used for
displaying error messages.

Reviewed-by: Rami Ylimäki <rami.ylimaki@vincit.fi>
Reviewed-by: Uli Schlachter <psychon@znc.in>
Signed-off-by: Arvind Umrao <arvind.umrao@oracle.com>