The Debian packaging of libcsfml is maintained in git, using the
merging workflow described in dgit-maint-merge(7).  There isn't a
patch queue that can be represented as a quilt series.

A detailed breakdown of the changes is available from their canonical
representation - git commits in the packaging repository.  For
example, to see the changes made by the Debian maintainer in the first
upload of upstream version 1.2.3, you could use:

    % git clone https://git.dgit.debian.org/libcsfml
    % cd libcsfml
    % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'

(If you have dgit, use `dgit clone libcsfml`, rather than plain
`git clone`.)

A single combined diff, containing all the changes, follows.
--- libcsfml-2.6.0.orig/doc/CMakeLists.txt
+++ libcsfml-2.6.0/doc/CMakeLists.txt
@@ -31,7 +31,7 @@ configure_file(${DOXYGEN_INPUT_DIR}/doc/
 configure_file(${DOXYGEN_INPUT_DIR}/doc/doxygen.css ${DOXYGEN_OUTPUT_DIR}/html/doxygen.css COPYONLY)
 
 # target setup
-add_custom_target(doc ALL
+add_custom_target(doc
                   COMMAND ${CMAKE_COMMAND} -E echo_append "Building API Documentation..."
                   COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYGEN_CONFIGURED_INPUT}
                   COMMAND ${CMAKE_COMMAND} -E echo "Done."
