eina - add prefetch macros to map to compiler builtins if they exist

this allows you to portably use prefetch compiler builtins. this adds
EINA_PREFETCH(), EINA_PREFETCH_WRITE(), EINA_PREFETCH_NOCACHE() and
EINA_PREFETCH_NOCACHE_WRITE() macros to do this that are "nothing" if
your compiler doesnt support it. of course it also requires your
compielr compile instructions for your architecture and it can only do
so if the architecture it compiles for has these instructions, so be
aware.

@feat

src/lib/eina/eina_types.h

@@ -133,6 +133,18 @@
 #ifdef EINA_SENTINEL
 # undef EINA_SENTINEL
 #endif
+#ifdef EINA_PREFETCH
+# undef EINA_PREFETCH
+#endif
+#ifdef EINA_PREFETCH_WRITE
+# undef EINA_PREFETCH_WRITE
+#endif
+#ifdef EINA_PREFETCH_NOCACHE
+# undef EINA_PREFETCH_NOCACHE
+#endif
+#ifdef EINA_PREFETCH_NOCACHE_WRITE
+# undef EINA_PREFETCH_NOCACHE_WRITE
+#endif
 
 #ifdef __GNUC__
 
@@ -181,6 +193,10 @@
 #  define EINA_UNLIKELY(exp)    __builtin_expect((exp), 0)
 #  define EINA_LIKELY(exp)      __builtin_expect((exp), 1)
 #  define EINA_SENTINEL __attribute__((__sentinel__))
+#  define EINA_PREFETCH(arg) __builtin_prefetch(arg)
+#  define EINA_PREFETCH_WRITE(arg) __builtin_prefetch(arg, 1)
+#  define EINA_PREFETCH_NOCACHE(arg) __builtin_prefetch(arg, 0, 0)
+#  define EINA_PREFETCH_NOCACHE_WRITE(arg) __builtin_prefetch(arg, 1, 0)
 # else
 #  define EINA_PRINTF(fmt, arg)
 #  define EINA_SCANF(fmt, arg)
@@ -190,6 +206,10 @@
 #  define EINA_UNLIKELY(exp) exp
 #  define EINA_LIKELY(exp)   exp
 #  define EINA_SENTINEL
+#  define EINA_PREFETCH(arg)
+#  define EINA_PREFETCH_WRITE(arg)
+#  define EINA_PREFETCH_NOCACHE(arg)
+#  define EINA_PREFETCH_NOCACHE_WRITE(arg)
 # endif
 
 #elif defined(_MSC_VER)
@@ -211,6 +231,10 @@
 # define EINA_UNLIKELY(exp) exp
 # define EINA_LIKELY(exp)   exp
 # define EINA_SENTINEL
+# define EINA_PREFETCH(arg)
+# define EINA_PREFETCH_WRITE(arg)
+# define EINA_PREFETCH_NOCACHE(arg)
+# define EINA_PREFETCH_NOCACHE_WRITE(arg)
 
 #elif defined(__SUNPRO_C)
 # define EINA_UNUSED
@@ -236,6 +260,10 @@
 # define EINA_UNLIKELY(exp) exp
 # define EINA_LIKELY(exp)   exp
 # define EINA_SENTINEL
+# define EINA_PREFETCH(arg)
+# define EINA_PREFETCH_WRITE(arg)
+# define EINA_PREFETCH_NOCACHE(arg)
+# define EINA_PREFETCH_NOCACHE_WRITE(arg)
 
 #else /* ! __GNUC__ && ! _MSC_VER && ! __SUNPRO_C */
 
@@ -322,9 +350,59 @@
  * @def EINA_SENTINEL
  * @brief Attribute from gcc to prevent calls without the necessary NULL
  * sentinel in certain variadic functions
- * @since 1.7.0
+ * @since 1.7
  */
 # define EINA_SENTINEL
+
+/**
+ * @def EINA_PREFETCH
+ * @brief Hints that the pointer @parg needs to be pre-fetched into cache
+ * This hints to the compiler to probably issue a prefetch command for the
+ * memory address @p arg and ensure it goes into all levels of cache. For
+ * just writing to an address look at EINA_PREFETCH_WRITE().
+ * Note that the pointer @p arg does not have to be a valid pointer and
+ * will not cause any exceptions (like segfaults) if it is invalid.
+ * @since 1.19
+ */
+# define EINA_PREFETCH(arg)
+
+/**
+ * @def EINA_PREFETCH_WRITE
+ * @brief Hints that the pointer @parg needs to be pre-fetched into cache
+ * This hints to the compiler to probably issue a prefetch command for the
+ * memory address @p arg and ensure it goes into all levels of cache. This
+ * specifically indicates that the address is going to be written to as
+ * opposed to being read from as with EINA_PREFETCH().
+ * Note that the pointer @p arg does not have to be a valid pointer and
+ * will not cause any exceptions (like segfaults) if it is invalid.
+ * @since 1.19
+ */
+# define EINA_PREFETCH_WRITE(arg)
+
+/**
+ * @def EINA_PREFETCH_NOCACHE
+ * @brief Hints that the pointer @parg needs to be pre-fetched into cache
+ * This hints to the compiler to probably issue a prefetch command for the
+ * memory address @p arg and ensure it goes into just the closest(l1) cache.
+ * For just writing to an address look at EINA_PREFETCH_WRITE_NOCACHE().
+ * Note that the pointer @p arg does not have to be a valid pointer and
+ * will not cause any exceptions (like segfaults) if it is invalid.
+ * @since 1.19
+ */
+# define EINA_PREFETCH_NOCACHE(arg)
+/**
+ * @def EINA_PREFETCH_WRITE_NOCACHE
+ * @brief Hints that the pointer @parg needs to be pre-fetched into cache
+ * This hints to the compiler to probably issue a prefetch command for the
+ * memory address @p arg and ensure it goes into just the closest(l1) cache.
+ * This specifically indicates that the address is going to be written to as
+ * opposed to being read from as with EINA_PREFETCH_NOCACHE().
+ * Note that the pointer @p arg does not have to be a valid pointer and
+ * will not cause any exceptions (like segfaults) if it is invalid.
+ * @since 1.19
+ */
+# define EINA_PREFETCH_NOCACHE_WRITE(arg)
+
 #endif /* ! __GNUC__ && ! _WIN32 && ! __SUNPRO_C */
 
 /**