pico_malloc.c doesn't include pico/malloc.h

[geurtv]

pico_malloc.c doesn't include pico/malloc.h (directly or indirectly). This means PICO_USE_MALLOC_MUTEX will always be 0 even with pico_multicore and PICO_MALLOC_PANIC now defaults to 0 instead of 1.

[geurtv]

Additionally in pico_malloc.c, when pico/malloc.h is included PICO_DEBUG_MALLOC is always on because

#ifdef PICO_DEBUG_MALLOC

is used instead of

#if PICO_DEBUG_MALLOC

[kilograham]

Spooky; i just noticed this last night!

[kilograham]

merged to develop