Add documentation

docs/CMakeLists.txt

@@ -0,0 +1,66 @@
+SET (CODES
+web/bootstrap/doxy-boot.js
+web/bootstrap/footer.html
+web/bootstrap/header.html
+web/bootstrap/customdoxygen.css
+offcanvas.css
+offcanvas.js
+solarized-light.css
+theme.css
+yap.css
+bootstrap.min.css
+bootstrap.min.js
+font-awesome.min.css
+jquery-2.0.3.min.js
+application.js
+pygments.css
+misc/icons/yap_64x64x32.png 
+misc/icons/yap_256x256x32.png
+misc/icons/yap_128x128x32.png
+misc/icons/yap_48x48x32.png
+  )
+
+SET (DOCS
+builtins.md
+chr.md
+clpqr.md
+download.md
+extensions.md
+fli.md
+install.md
+packages.md
+run.md
+swi.md
+syntax.md
+yap.md
+  )
+  
+  
+
+# add a target to generate API documentation with Doxygen
+
+find_package(Doxygen)
+option(WITH_DOCUMENTATION "Create and install the HTML based API documentation (requires Doxygen)" ${DOXYGEN_FOUND})
+
+if(WITH_DOCUMENTATION)
+    if(NOT DOXYGEN_FOUND)
+        message(FATAL_ERROR "Doxygen is needed to build the documentation.")
+    endif()
+
+    set(doxyfile_in ${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile.in)
+    set(doxyfile ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile)
+
+    
+   configure_file(${doxyfile_in} ${doxyfile} @ONLY)
+
+     add_custom_target(doc
+        COMMAND ${DOXYGEN_EXECUTABLE} ${doxyfile}
+        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+        COMMENT "Generating API documentation with Doxygen"
+        VERBATIM)
+
+    install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/html DESTINATION ${docdir})
+    install(FILES  ${CODES} DESTINATION ${docdir})
+
+  endif()
+