[exosphere] Map the crt0 too

Use and adapt the UART driver from hekate/hwinit

Add debug region to mapped memory

Implement and use set_memory_registers_enable_mmu

Implement the rest of smcCpuSuspend with skeleton SE API calls.

Use provided __libc_init_array and __libc_fini_array, bugfixes

Rewrite the memory map-related code... ...

...other style fixes, etc.

memory_map: Remove unnecessary const ...

Since the return value isn't a pointer thing doesn't have much use.

Failed attempt to fix loops not being unrolled, other fixes.

Move source files to src/, add Makefile, fix all build and linkage errors, etc.