Build: Fixes for Wmissing-field-initializers

Fixes for all module against missing-field-initializers
errors. Actually, many of those were not even needed or
used.
Kept the warning suppressed for the tests for
the moment. It's debatable, if we want to keep it for
tests forever though.
Also had to define CFLAGS for libtestutil.

Signed-off-by: Andreas Fuchs <andreas.fuchs@sit.fraunhofer.de>
diff --git a/src/tss2-esys/api/Esys_ContextLoad.c b/src/tss2-esys/api/Esys_ContextLoad.c
index 196411b..9517080 100644
--- a/src/tss2-esys/api/Esys_ContextLoad.c
+++ b/src/tss2-esys/api/Esys_ContextLoad.c
@@ -123,7 +123,7 @@
     TSS2_RC r;
     LOG_TRACE("context=%p, context=%p",
               esysContext, context);
-    IESYS_CONTEXT_DATA esyscontextData = {0};
+    IESYS_CONTEXT_DATA esyscontextData;
     TPMS_CONTEXT tpmContext;
 
     /* Check context, sequence correctness and set state to error for now */
@@ -225,7 +225,7 @@
     if (r != TSS2_RC_SUCCESS)
         return r;
 
-    IESYS_CONTEXT_DATA esyscontextData = {0};
+    IESYS_CONTEXT_DATA esyscontextData;
     size_t offset = 0;
     r = Tss2_MU_IESYS_CONTEXT_DATA_Unmarshal(&esysContext->in.ContextLoad.context->contextBlob.buffer[0],
                                                  sizeof(IESYS_CONTEXT_DATA),