docs: Move the grand SECTION

Move it to a separate page so the difference between `g_rand_*()` and
`g_random_*()` can be explained.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Helps: #3037

glib/grand.c

@@ -62,57 +62,6 @@
 #include <process.h> /* For getpid() */
 #endif
 
-/**
- * SECTION:random_numbers
- * @title: Random Numbers
- * @short_description: pseudo-random number generator
- *
- * The following functions allow you to use a portable, fast and good
- * pseudo-random number generator (PRNG).
- * 
- * Do not use this API for cryptographic purposes such as key
- * generation, nonces, salts or one-time pads.
- *
- * This PRNG is suitable for non-cryptographic use such as in games
- * (shuffling a card deck, generating levels), generating data for
- * a test suite, etc. If you need random data for cryptographic
- * purposes, it is recommended to use platform-specific APIs such
- * as `/dev/random` on UNIX, or CryptGenRandom() on Windows.
- *
- * GRand uses the Mersenne Twister PRNG, which was originally
- * developed by Makoto Matsumoto and Takuji Nishimura. Further
- * information can be found at
- * [this page](http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html).
- *
- * If you just need a random number, you simply call the g_random_*
- * functions, which will create a globally used #GRand and use the
- * according g_rand_* functions internally. Whenever you need a
- * stream of reproducible random numbers, you better create a
- * #GRand yourself and use the g_rand_* functions directly, which
- * will also be slightly faster. Initializing a #GRand with a
- * certain seed will produce exactly the same series of random
- * numbers on all platforms. This can thus be used as a seed for
- * e.g. games.
- *
- * The g_rand*_range functions will return high quality equally
- * distributed random numbers, whereas for example the
- * `(g_random_int()%max)` approach often
- * doesn't yield equally distributed numbers.
- *
- * GLib changed the seeding algorithm for the pseudo-random number
- * generator Mersenne Twister, as used by #GRand. This was necessary,
- * because some seeds would yield very bad pseudo-random streams.
- * Also the pseudo-random integers generated by g_rand*_int_range()
- * will have a slightly better equal distribution with the new
- * version of GLib.
- *
- * The original seeding and generation algorithms, as found in
- * GLib 2.0.x, can be used instead of the new ones by setting the
- * environment variable `G_RANDOM_VERSION` to the value of '2.0'.
- * Use the GLib-2.0 algorithms only if you have sequences of numbers
- * generated with Glib-2.0 that you need to reproduce exactly.
- */
-
 /**
  * GRand:
  *