1. Make sure Pico SDK libraries have the correct dependencies on other SDK libraries
2. Pico SDK libraries all have _headers variants to include the headers. This may facilitate building user STATIC libraries without
pulling in SDK code, though care will still need to be taken w.r.t. values of #defines
3. Make sure the _headers versions also have the correct dependencies
Note: There are a few exceptions to 1. for some non code libraries like pico_standard_link and pico_cxx_options
When using a linker script which does not provide a .time_critical.
section that is marked "ax" and wrongly define
PICO_INT64_OPS_IN_RAM=1 this would generate a malformed
executable with strange runtime bugs in the worst case.
* 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
