merge libmaple docs ("leaflabs-docs") into ./docs

In the past, libample documentation was forked out of this repository
because the documentation had increased in scope. For the librambutan,
and the rambutan project in general, we will try to keep documentation
closer to the source code, so the librambutan-specific documentation
should live here. Other sections of leaflabs-docs will be culled in a
following commit.

This merge attempts to maintain history by using a subtree strategy.
Followed directions at:

    http://nuclearsquid.com/writings/subtree-merging-and-you/

Full history for files should be accessible using the "--follow" flag to
git log, eg:

    git log --follow docs/source/adc.rst

It should be possible to pull patches from leaflabs-docs with:

    git pull -s subtree leaflabs-docs master

... at least until the docs in this repository diverge significantly.

1 files changed, 54 insertions, 0 deletions

diff --git a/docs/source/lang/cpp/define.rst b/docs/source/lang/cpp/define.rst
new file mode 100644
index 0000000..b22085f
--- /dev/null
+++ b/docs/source/lang/cpp/define.rst
@@ -0,0 +1,54 @@
+.. highlight:: cpp
+
+.. _lang-define:
+
+``#define``
+===========
+
+``#define`` is a useful C and C++ feature that allows the programmer
+to give a name to a constant value before the program is compiled.
+The compiler will replace references to these constants with the
+defined value at compile time.
+
+This can have some unwanted side effects.  In general, the :ref:`const
+<lang-const>` keyword is preferred for defining constants.
+
+Syntax
+------
+
+The following line would define the name ``MY_CONSTANT`` to have value
+``value``::
+
+    #define MY_CONSTANT value
+
+Note that the ``#`` is necessary.  It is usually good style for the
+name to be capitalized, although this is not required.
+
+There is no semicolon after the #define statement. If you include one,
+the compiler will likely throw cryptic errors in unrelated places.
+That is, **don't do this**::
+
+    // DON'T DO THIS! THE SEMICOLON SHOULDN'T BE THERE!
+    #define NAME value;
+
+Similarly, including an equal sign after the ``#define`` line will
+also generate a cryptic compiler error further down the page.  That
+is, **don't do this, either**::
+
+    // DON'T DO THIS, EITHER! THE EQUALS SIGN SHOULDN'T BE THERE!
+    #define NAME = value
+
+Example
+-------
+
+ ::
+
+    #define MAPLE_LED_PIN 13
+    // The compiler will replace any mention of MAPLE_LED_PIN with
+    // the value 13 at compile time.
+
+See Also
+--------
+-  :ref:`const <lang-const>`
+
+.. include:: /arduino-cc-attribution.txt