newlib: add an option to combine some locks.
newlib: add an option to combine some locks.

The locks are using a bit of the limited ram. It's probably fine to combine some
of these to use the same mutex, and this patch does so for the set initialized
early. The file locks will still be separate, and dynamically created, so a
thread blocking on them will not deadlock all uses of newlib that need a lock.

SuperHouse/esp-open-rtos,ourairquality/esp-open-rtos,SuperHouse/esp-open-rtos,urx/esp-open-rtos,UncleRus/esp-open-rtos,urx/esp-open-rtos,urx/esp-open-rtos,UncleRus/esp-open-rtos,ourairquality/esp-open-rtos,SuperHouse/esp-open-rtos,SuperHouse/esp-open-rtos,UncleRus/esp-open-rtos,ourairquality/esp-open-rtos,SuperHouse/esp-open-rtos,urx/esp-open-rtos,Zaltora/esp-open-rtos,UncleRus/esp-open-rtos,bhuvanchandra/esp-open-rtos,Zaltora/esp-open-rtos,UncleRus/esp-open-rtos,UncleRus/esp-open-rtos,Zaltora/esp-open-rtos,Zaltora/esp-open-rtos,bhuvanchandra/esp-open-rtos,SuperHouse/esp-open-rtos,Zaltora/esp-open-rtos,ourairquality/esp-open-rtos,ourairquality/esp-open-rtos,ourairquality/esp-open-rtos,Zaltora/esp-open-rtos,bhuvanchandra/esp-open-rtos,urx/esp-open-rtos,bhuvanchandra/esp-open-rtos,urx/esp-open-rtos