Fix minor issues found by static analyzers

Avoid possible NULL dereferences of error_msg

Fixes #155.

Signed-off-by: Martin Milata <mmilata@redhat.com>
Signed-off-by: Jakub Filak <jfilak@redhat.com>

Fix insecure string formatting

core_unwind_elfutils.c: In function 'sr_parse_coredump':
core_unwind_elfutils.c:169:13: error: format not a string literal and no format arguments [-Werror=format-security]
             set_error(thread_arg.error_msg);
             ^

Signed-off-by: Martin Milata <mmilata@redhat.com>
Fix the compat version of duphash generation

sr_thread_get_duphash() must return NULL for oopses having no reliable
frame.

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Fix parsing of invalid syntax Python exceptions

Closes #168

Signed-off-by: Jakub Filak <jfilak@redhat.com>

mmilata: commit msg typo
gdb: fix parsing of ppc64 stacktraces

Fixes rhbz#1119072.

Signed-off-by: Martin Milata <mmilata@redhat.com>
unwind: limit the number of frames unwound

Fixes rhbz#1133907.

Signed-off-by: Martin Milata <mmilata@redhat.com>
Add authentication data support in uReport

Support authentication data in uReport

We need this for 'machine id' element which should be present only if
users wishes to it.

The authentication entries are string based, key value pairs (JSON
string elements).

The entries are enclosed in an envelope object called 'auth'.

Example:

"auth" : {   "machineid" : "deadbeaf"
         }

Fixes #171

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Signed-off-by: Martin Milata <mmilata@redhat.com>

mmilata: s/custom/auth/g, python bindings

tests: add a test for uReport auth data

Related to #171

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Signed-off-by: Martin Milata <mmilata@redhat.com>

mmilata: python test

ureport: fix indentation of 'auth' key in JSON

Fixes a bug in commit 189f7adbba9c38bd434c30e7d0c07b546c373312

Related to #171

Signed-off-by: Jakub Filak <jfilak@redhat.com>