RTOS - fix for main thread id might not be 0x02

[0xc0170]

Fixes #2059. As reported, if timer thread is not created, the main thread
id is 0x01. We introduce MAIN_THREAD_ID macro to define the id. We shall consider,
if we keep this in a variable.

I placed MAIN_THREAD_ID in cmsis_os.h as that header is safe to include within RTX, not like
RTX_Config.h or RTX_CM_Lib.h). I reported an issue to cmsis team about this inclusion mess within RTX.

tested with K64F with default config:

+--------+------------+-----------+---------+-------------------------+--------------------+---------------+-------+
| Result | Target     | Toolchain | Test ID | Test Description        | Elapsed Time (sec) | Timeout (sec) | Loops |
+--------+------------+-----------+---------+-------------------------+--------------------+---------------+-------+
| OK     | K64F[f3f7] | ARM       | RTOS_1  | Basic thread            |       11.36        |       15      |  1/1  |
| OK     | K64F[f3f7] | ARM       | RTOS_3  | Semaphore resource lock |        8.45        |       20      |  1/1  |
| OK     | K64F[f3f7] | ARM       | RTOS_5  | Queue messaging         |        2.4         |       20      |  1/1  |
| OK     | K64F[f3f7] | ARM       | RTOS_7  | Timer                   |       11.33        |       15      |  1/1  |
| OK     | K64F[f3f7] | ARM       | RTOS_8  | ISR (Queue)             |        6.41        |       20      |  1/1  |
+--------+------------+-----------+---------+-------------------------+--------------------+---------------+-------+

+--------+------------+-----------+---------+-------------------------+--------------------+---------------+-------+
| Result | Target     | Toolchain | Test ID | Test Description        | Elapsed Time (sec) | Timeout (sec) | Loops |
+--------+------------+-----------+---------+-------------------------+--------------------+---------------+-------+
| OK     | K64F[f3f7] | GCC_ARM   | RTOS_1  | Basic thread            |       11.37        |       15      |  1/1  |
| OK     | K64F[f3f7] | GCC_ARM   | RTOS_3  | Semaphore resource lock |        8.5         |       20      |  1/1  |
| OK     | K64F[f3f7] | GCC_ARM   | RTOS_5  | Queue messaging         |        2.38        |       20      |  1/1  |
| OK     | K64F[f3f7] | GCC_ARM   | RTOS_7  | Timer                   |       11.36        |       15      |  1/1  |
| OK     | K64F[f3f7] | GCC_ARM   | RTOS_8  | ISR (Queue)             |        6.45        |       20      |  1/1  |
+--------+------------+-----------+---------+-------------------------+--------------------+---------------+-------+

Our tests are multithreaded thus NOT SUPPORTED once I switch to small default build. I run just main thread with blinky to blink LED, working.

@gdhamp Please verify this patch.

[geky]

+1, also +1 for reporting the inclusion mess.

Is cmsis_os.h the appropriate place for rtx defines accessible from other code? Perhaps we should move the overrides in RTX_Conf_CM.c out to cmsis_os.h then?

[hamslabs]

+1 - Looks good and thanks for the fast response.