Move the memory allocation/deallocation routines to the common library

They are still used slightly differently in the encoder and decoder;
the decoder uses plain functions while the encoder uses one object
keeping track of the number of allocated bytes, and keeping track
of the requested alignment.

codec/decoder/core/src/decoder.cpp

@@ -51,7 +51,7 @@
 #include "expand_pic.h"
 #include "decode_slice.h"
 #include "error_concealment.h"
-#include "mem_align.h"
+#include "memory_align.h"
 
 namespace WelsDec {