Merge branch 'bugfix/spurious_uninitialized_mux_notice' into 'master'

Add static initializers for muxes, add mutex init to vPortCPUAcquireMutex

We still have some ERROR: vPortCPUAcquireMutex: mux 0x3ffc01cc is uninitialized (0x0)!  errors. I'd like to fix those by giving muxes as used in critical regions an initializer, so they can get initialized at program load. This is FreeRTOS core code, I'd like someone to review it before I commit it.

See merge request !10