The flag hides errors. But we want unit tests to be correct in order
to reveal errors in the main code.
The patch removes tests_unittests_unittests_CFLAGS which makes autotools
use AM_CFLAGS instead. Therefore, unit tests are built with flags
derived from configure.ac.
Move `p_sha1_hash()` from `common.c` to `xmpp/stanza.c` as it is only
used in this file and now depends on libstrophe so xmpp is a better
namespace folder.
Renaming it as `_stanza_create_sha1_hash()`. And making static since
only used here.
The function cannot be tested in the unit tests anymore.
Once functional tests are working again we should write a test for the
sha1 functionality.
