* Fix various non-GCC warnings (no effect on GCC)
* Reduce use of typeof since non GCC compilers may not support it
* Introduce PICO_C_COMPILER_IS_GNU, PICO_C_COMPILER_IS_CLANG, PICO_C_COMPILER_IS_IAR to CMake as if (CMAKE_C_COMPILER_ID STREQUAL "xxx") is a bit verbose
* Use "unified_asm" macro for all inline asm (it is "volatile __asm" on GNU with a .syntex unified)
* Use NOLOAD instead of COPY in linker scripts (arguably more correct anyway)
* Use the same style for setting _etext in all 4 linker scripts (to the beginning of .data). Clang aligns .data on a 16 byte boundary. Note ideally we'd
add a new symbol __data_source, however that would break backwards compatibility with existing user linker scripts
* Use "a" for .stack, .heap sections because clang complains otherwise, and they are explicitly NOLOAD anyway
* Avoid duplicating __sev, __wfe, __wfi which Clang sometimes seems to provide as built-ins
* Add missing kitchen_sink_blocked_ram binary
* Allow build with LLVM Embedded Toolchain Form ARM v 14.0.0 (unsupported atm)
Add a -nostdlib specifically for the check to ensure that it builds
successfully.
The -nostdlib isn't needed normally, because linking against the pico
SDK will add in definitions for the previously-missing function
* 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
* Change some cmake output to DEBUG level
Make SDK build more consistent with other libraries (use an INTERFACE marker library for inclusion tests)
Add PICO_SDK_PRE_LIST_FILES, PICO_SDK_POST_LIST_FILES build vars
* fix typo
* remove leftover debugging message
* pico_stdio_usb: be more explicit about includes, fix warning (#257)
* pico_base: NDEBUG backwards for absolute_time_t (#255)
* pico_util: missing extern C in queue.h (#249)
* build: remove -march which was masking -mcpu, now SVC available (#253)
