SyroComp_CompBlock: Prevent stack buffer overflow

[benwiley4000]

Closes #18.

I found a stack buffer overflow in SyroComp_CompBlock that didn't seem to result in any bugs when I compiled code with GCC.. however I consistently ran into problems when compiling to WebAssembly with Emscripten.

In this code:

volcasample/syro/korg_syro_comp.c

Lines 394 to 403 in b0ed615

	/*----- wrtie bit-base ------*/
	j = 0;
	for (i=0; i<16; i++) {
	if (pBitBase[j]==i) {
	BitHead[i] = j++;
	SyroComp_WriteBit(&wp, (uint32_t)(i-1), 4);
	} else {
	BitHead[i] = -1;
	}
	}

We can see that once j has been incremented to 4, the index 4 of BitBase (which doesn't exist) will be checked for the remainder of the loop. If the out of bounds memory happens to match i by accident, then we will get a false positive and write incorrect data.

Adding the index guard in this pull request solves the problem and makes my tests pass (for both GCC and Emscripten).