Fixes:
    /sssd/src/tools/sss_override.c: In function ‘override_user_import’:
    /sssd/src/tools/sss_override.c:1471: warning: declaration of ‘exit’ shadows a global declaration
    /usr/include/stdlib.h:544: warning: shadowed declaration is here
    /sssd/src/tools/sss_override.c: In function ‘override_group_import’:
    /sssd/src/tools/sss_override.c:1737: warning: declaration of ‘exit’ shadows a global declaration
    /usr/include/stdlib.h:544: warning: shadowed declaration is here

The handling of sbus requests in Data Provider was extremely duplicated,
resulting in copy-paste errors. This patch adds several helpers that
reduce code duplication.

libdbus abort()s when a string argument is not valid UTF-8. Since the
arguments sometimes come from untrusted sources, it's better to check
the string validity explicitly.

https://fedorahosted.org/sssd/ticket/2861

Messages passed from Data Provider to responder must be valid UTF-8
strings. Because providers might not be completely under our control,
we need to check if the messages we receive are valid UTF-8 and if they
are not, use a fallback.

Resolves:
    https://fedorahosted.org/sssd/ticket/2861

All back end requests were using pam_strerror() to print additional info
about why request failed. Since pam_strerror() returns localized message
and we don't know the locale beforehand, this message failed to be
transferred through D-Bus, resulting in a crash.

Fail CI coverage build, if make-check stage fails. Previously make-check
stage failures were ignored for coverage build for the sake of
collecting coverage data in any case. However, catching extra test
failures seems more important than getting coverage data in all cases,
thus the change.

Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>

It's fixed in upstream gcc >= 4.6.0

Resolves:
https://fedorahosted.org/sssd/ticket/2819

Reviewed-by: Nikolai Kondrashov <Nikolai.Kondrashov@redhat.com>