Build istl.pdf

[[Imported from SVN: r1575]]

doc/CMakeLists.txt

 add_subdirectory("doxygen")
 add_subdirectory("comm")
+if(LATEX_USABLE)
+  ADD_LATEX_DOCUMENT(istl.tex FATHER_TARGET doc
+    BIB_FILES istl.bib  DEFAULT_SAFEPDF IMAGES blockstructure.eps)
+  create_doc_install(${CMAKE_CURRENT_BINARY_DIR}/istl.pdf
+    share/doc/dune-istl/)
+endif(LATEX_USABLE)