[iQue] Import libultra audio library files (#2433)

Note about comments in these files:
The libultra audio library was originally available to developers in
source code form, unlike most of libultra. These files are based on
these source code forms, adapted to meet the style of this project.
The comments in the files as of this commit are, apart from the style,
comments from the original SGI authors.

include/ultra64.h

@@ -70,7 +70,6 @@ void* osViGetNextFramebuffer(void);
 void osCreatePiManager(OSPri pri, OSMesgQueue* cmdQueue, OSMesg* cmdBuf, s32 cmdMsgCnt);
 void __osDevMgrMain(void* arg);
 s32 __osPiRawStartDma(s32 dir, u32 cartAddr, void* dramAddr, size_t size);
-u32 osVirtualToPhysical(void* vaddr);
 void osViBlack(u8 active);
 s32 __osSiRawReadIo(void* devAddr, u32* dst);
 OSId osGetThreadId(OSThread* thread);

include/ultra64/convert.h

@@ -15,4 +15,6 @@
 #define OS_PHYSICAL_TO_K0(x)    (void*)(((u32)(x)+0x80000000))
 #define OS_PHYSICAL_TO_K1(x)    (void*)(((u32)(x)+0xA0000000))
 
+u32 osVirtualToPhysical(void* vaddr);
+
 #endif