* Add missing DREQ_s
* store actual clock frequency in clock_configure (fixes#368)
* use dma DREQ values defined in dreqs/dma.h
* Fix hw_is_claimed, and add xxx_is_claimed APIs
* Add some PIO irq helper methods
* Add DMA channel IRQ status getter and clear methods
* Implement the correct PIO IRQ status/clear methods (good to have methods here as the h/w interrupt registers are super confusing)
* fix pico_multicore dependencies
* add missing wrapper func __aeabi_f2d
* Further DMA/PIO IRQ API cleanup (and review fixes)
* add PICO_INT64_OPS_IN_RAM flag
Fixes the following warning when building for host
```
[...]/pico-sdk/src/common/pico_time/time.c: In function 'alarm_pool_dump_key':
[...]/pico-sdk/src/common/pico_time/time.c:282:15: warning: format '%ld' expects argument of type 'long int', but argument 2 has type 'uint64_t' {aka 'long long unsigned int'} [-Wformat=]
printf("%ld", to_us_since_boot(get_entry(pool, id)->target));
~~^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
%I64d
```
- Add recursive_mutex
- Make all locking primitives and sleep use common overridable wait/notify support to allow RTOS
implementations to replace WFE/SEV with something more appropriate
- Add busy_wait_ms
