extend module documentation

modules/default_build_paths.cmake

@@ -1,2 +1,17 @@
+#.rst:
+#
+# Sets binary and library output directories to ${PROJECT_BINARY_DIR}/bin
+# and ${PROJECT_BINARY_DIR}/lib, respectively.
+#
+# Variables modified::
+#
+#   CMAKE_RUNTIME_OUTPUT_DIRECTORY
+#   CMAKE_LIBRARY_OUTPUT_DIRECTORY
+#
+# Example autocmake.cfg entry::
+#
+#   [default_build_paths]
+#   source: https://github.com/scisoft/autocmake/raw/master/modules/default_build_paths.cmake
+
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/bin)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/lib)