Move libultra function declarations to libultra headers (#1196)

* Delete unused headers

* Move PR and io to ultra64

* move headers to ultra64

* more cleanups

* more reorganizing

* i think that should be all

* format

* ifdef guards cleanup

* Add IO_READ and IO_WRITE macros for future use

* warnings

* review

Co-authored-by: Tharo <17233964+Thar0@users.noreply.github.com>

* warnings again

* warn

* ifdef guards

* fix merge

* fix merge

* fix merge

* bss

* padutils.h

* bss

* bss

* bss

* fix merge

* bss

* bss

* bss

* fix merge

* fixes

* fixes

* bss

* bss

* fix merge

* fix

* fix

* fix includepaths

* fix paths

* bss

* fix

* ultra64/ -> PR/

* header guards

* fix ehader guards

* fix

* fix++

* format

* bss is borken

* prevent 2

* :despair:

* bss

* rename assert to dbg_hungup

* fix

* a

* fix

* bss

* fix

* bss

* bss

---------

Co-authored-by: Tharo <17233964+Thar0@users.noreply.github.com>

include/libc/string.h

@@ -0,0 +1,12 @@
+#ifndef LIBC_STRING_H
+#define LIBC_STRING_H
+
+#include "libc/stddef.h"
+
+
+const char* strchr(const char* s, int c);
+size_t strlen(const char* s);
+void* memcpy(void* s1, const void* s2, size_t n);
+
+
+#endif