Clarify link between number and cdata (#3050)

* Clarify the connection between number and cdata
* Adjust table widths
* Mention decimal among number field index types

Resolves #3049
Resolves #3040

Author: patiencedaur

doc/book/box/data_model.rst

@@ -127,7 +127,7 @@ Lua versus MsgPack
 ..  container:: table
 
     ..  list-table::
-        :widths: 15 20 30 35
+        :widths: 15 30 15 40
         :header-rows: 1
 
         *   -   Scalar / compound
@@ -150,6 +150,10 @@ Lua versus MsgPack
             -   integer
             -   `number`_
             -   ``12345``
+        *   -   scalar
+            -   integer
+            -   `cdata`_
+            -   ``12345``
         *   -   scalar
             -   float64 (double)
             -   `number`_
@@ -291,6 +295,9 @@ Here are examples of numbers using regular notation, exponential notation,
 the ULL suffix and the ``tonumber64`` function:
 ``-55``, ``-2.7e+20``, ``100000000000000ULL``, ``tonumber64('18446744073709551615')``.
 
+You can also use the ``ffi`` module to specify a C type to cast the number to.
+In this case, the number will be stored as `cdata`_.
+
 ..  _index-box_decimal:
 
 **decimal**. The Tarantool decimal type is stored as a MsgPack ext (Extension).
@@ -437,7 +444,8 @@ Full information is in section
             -   TREE or HASH
         *   -   ``'number'``
             -   :ref:`number <index-box_number>`, which may include
-                :ref:`integer <index-box_integer>` or :ref:`double <index-box_double>` values
+                :ref:`integer <index-box_integer>`, :ref:`double <index-box_double>`,
+                or :ref:`decimal <index-box_decimal>` values
             -   TREE or HASH
         *   -   ``'decimal'``
             -   :ref:`decimal <index-box_decimal>`

locale/ru/LC_MESSAGES/book/box/data_model.po

@@ -711,10 +711,10 @@ msgstr "``'number'``"
 
 msgid ""
 ":ref:`number <index-box_number>`, which may include :ref:`integer <index-"
-"box_integer>` or :ref:`double <index-box_double>` values"
+"box_integer>`, :ref:`double <index-box_double>`, or :ref:`decimal <index-box_decimal>` values"
 msgstr ""
 ":ref:`number <index-box_number>`, может включать в себя значения типа "
-":ref:`integer <index-box_integer>` или :ref:`double <index-box_double>`"
+":ref:`integer <index-box_integer>`, :ref:`double <index-box_double>` или :ref:`decimal <index-box_decimal>`"
 
 msgid "``'decimal'``"
 msgstr "``'decimal'``"