Setup to document entire project using doxygen.

New doc directory with config files and generated html, LaTeX/pdf.
Makefile provided for autogeneration and explanatory README.

The project structure is hostile to doxygen, which can't cope with functions
of the same name. Doxygen is run for each family separately, and separately
for LaTeX generation. Customized layout files sort of "integrate" HTML, and
separate pdfs are generated for each family. Not ideal but seems the best
solution until doxygen changes, if at all.

include/libopencm3/cm3/doc-cm3.h

@@ -0,0 +1,22 @@
+/** @mainpage libopencm3 Core CM3
+
+@version 1.0.0
+
+@date 14 September 2012
+
+API documentation for Cortex M3 core features.
+
+LGPL License Terms @ref lgpl_license
+*/
+
+/** @defgroup CM3_defines CM3 Defines
+
+@brief Defined Constants and Types for Cortex M3 core features
+
+@version 1.0.0
+
+@date 14 September 2012
+
+LGPL License Terms @ref lgpl_license
+*/
+