Memstuff (#1164)

* Un-fake a couple of matches in memory manip functions

* Document fmodf

* Un-fake a couple of matches in memory manip functions

* Document fmodf

* Rename functions and files

* Document memmove, memsets, memcpys

* Format

* Sort out some missing sizeofs

* Name fmodf

* Rename local variables

* size_t

* Use COBRA_SHADOW_TEX_SIZE

* Review

* Tweak the Doxyfile to remove @brief requirement

* Roman's review

* Fix a bug comment

* Change fmodf

src/code/__osMemset.c

@@ -0,0 +1,21 @@
+#include "global.h"
+
+/**
+ * memset: sets `len` bytes to `val` starting at address `dest`.
+ *
+ * @see There are two other memsets in this codebase, Lib_MemSet(), MemSet()
+ *
+ * @param dest address to start at
+ * @param val value to write (s32, but interpreted as u8)
+ * @param len number of bytes to write
+ *
+ * @return dest
+ */
+void* __osMemset(void* dest, s32 val, size_t len) {
+    u8* ptr = dest;
+
+    while (len--) {
+        *ptr++ = val;
+    }
+    return dest;
+}