Bump to v5.1.0-rc1+dev221

Update ReadMe

README.md

@@ -10,6 +10,25 @@ The autogenerated OSAL user's guide can be viewed at <https://github.com/nasa/cF
 
 ## Version History
 
+### Development Build: 5.1.0-rc1+dev221
+
+- Fixes `printf` format to correctly build in RTEMS-5.
+- **Deprecates `OS_fsBlocksFree()` and `OS_fsBytesFree()`** in favor of `OS_FileSysStatVolume()`.
+- Adds `Security.md` with instructions to report vulnerabilities.
+- Add `UtDebug` in `OS_printf` stub. Output the `OS_printf` input as a debug message from stub.
+- Documentation: Add note on `UtTest_Add` API. Nesting `UtTest_Add` from within an added test fails without error.
+- Unit Test: No more garbage characters written to test report log
+- Fix typo in `osapi.h` affecting C++ build. No other functional change
+- Unit Test: Rename `UT_ClearForceFail` as `UT_ClearDefaultValue`. Update the comments of `UT_SetDefaultReturnValue` to match the more general function.
+- Unit Test: Add test teardown failures to the test summary and changed the printout to use the same style as startup failures.
+- Unit Test: Removes no longer applicable `UT_CheckForOpenSockets` since the UT framework resets the state for each unit test.
+- Changes the file-create operation to read-write permissions to work on RTEMS
+- Unit Test: Fixes incorrect assertions in `network-api-test` to correctly check return values.
+- Unit Test: Generalizes queue timeout test to also test message queue functionality to validate settings and permissions to work with mqueues.
+- Implements `OS_time_t` with a single 64-bit tick counter rather than a split 32 bit seconds + 32 bit microseconds counter.
+- Unit Test: Installs the modules used in unit testing and adds removal of post-test, left-over files.
+- See <https://github.com/nasa/osal/pulls/767>
+
 ### Development Build: 5.1.0-rc1+dev184
 
 - Address issues with OSAL global table management:

src/os/inc/osapi-version.h

@@ -30,7 +30,7 @@
 /*
  * Development Build Macro Definitions
  */
-#define OS_BUILD_NUMBER   184
+#define OS_BUILD_NUMBER   221
 #define OS_BUILD_BASELINE "v5.1.0-rc1"
 
 /*