Travis: ignore GERRIT_CHANGE_ID

Change-Id: I68bcb455a02982a692fd94db008874097219d157
Signed-off-by: Pascal Brand <pascal.brand@st.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Add MSG() macro for traces

MSG() and MSG_RAW() macros are added.
They are the same as xMSG() and xMSG_RAW() existing macros, but are not
subject to dynamic trace level

Note that when the core trace level is 0, these macros are void.

This patch also fixes an issue with "printf" level.

Change-Id: Ibff6058d7e35d728a46878b345b6e0833c18aec1
Reviewed-on: https://gerrit.st.com/18102
Reviewed-by: Emmanuel MICHEL <emmanuel.michel@st.com>
Signed-off-by: Pascal Brand <pascal.brand@st.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Keep binary compatilities TEECore <--> TA

In case the core is compiled with
    CFG_TEE_TA_LOG_LEVEL=0
then TA cannot be compiled with CFG_TEE_TA_LOG_LEVEL!=0 because of the trace
function.

This patch implements stub trace functions in case of unsufficient trace level.
It also check
- TRACE_LEVEL < 0  instead of TRACE_LEVEL == 0
- TRACE_LEVEL >= 0 instead of TRACE_LEVEL != 0
to take into account negative trae levels

Change-Id: I7b4d2d576c50e103d9cf6f5b22f9f99a1ab96d6a
Signed-off-by: Pascal Brand <pascal.brand@st.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Update documentation/build_system.md

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>