Add doxygen comments to MSP's oneway malloc

sys/oneway-malloc/include/malloc.h

+/*
+ * Copyright (C) 2014 Freie Universität Berlin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @addtogroup  oneway_malloc
+ * @{
+ * @file        malloc.h
+ * @brief       A malloc implementation for MSP-430 boards without free.
+ *
+ * @details     The toolchain of MSP-430 does not contain malloc() and friends.
+ *              These functions provide the same interface as the stdlib functions,
+ *              but the option to free memory.
+ *
+ * @note        You should prefer statically allocated memory whenever possible.
+ *
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ * @author      René Kijewski <rene.kijewski@fu-berlin.de>
+ */
+
 #ifndef __MALLOC_H
 #define __MALLOC_H
 
 #include <stdlib.h>
 
+/**
+ * @brief       Allocation a block of memory.
+ * @param[in]   size   Size of the block to allocate in bytes.
+ * @returns     The new memory block. `NULL` if the "heap" is exhausted.
+ */
 void *malloc(size_t size);
+
+/**
+ * @brief       Allocated a new block of memory and move the existing content.
+ * @details     This function allocates a new block of memory and memcpy()s the content of the ond `ptr` there.
+ *
+ *              We do not know the size of the old block, so illegal reads would be likely,
+ *              if it was not for the fact that the memory heap up.
+ * @param[in]   ptr    Old memory block that was allocated with malloc(), calloc() or realloc().
+ * @param[in]   size   Size of the new block to allocted in bytes.
+ * @returns     The new memory block. `NULL` if the "heap" is exhausted.
+ */
 void *realloc(void *ptr, size_t size);
+
+/**
+ * @brief       Allocate a memory block and set all its content to zeroes.
+ * @details     Please see malloc() for more information.
+ * @note        This implementation of calloc() does not catch integer overflows
+ * @param[in]   size   One factor of the number of bytes to allocated.
+ * @param[in]   cnt    The other factor of the number of bytes to allocated.
+ * @returns     The new memory block. `NULL` if the "heap" is exhausted.
+ */
 void *calloc(int size, size_t cnt);
+
+/**
+ * @brief       This is a no-op.
+ * @details     You read correctly: This function does noting.
+ * @note        Keep in mind that this function does not free the memory. It does nothing.
+ * @param[in]   ptr   The ignored argument.
+ */
 void free(void *ptr);
 
 #endif /* __MALLOC_H */
+
+/**
+ * @}
+ */