[cmake][bugfix] Exclude hidden headers from header checks.

Previously hidden unix files were included in the headercheck.
Unfortunately  emacs(server) tends to produces files such as
.#<headername>. This broke the constructed Makefiles. This patch
excludes such files from the list and fixes the issue.

cmake/modules/Headercheck.cmake

@@ -4,7 +4,9 @@ macro(setup_headercheck)
   #glob for headers
   file(GLOB_RECURSE src_headers "src/*.hh")
   file(GLOB_RECURSE dune_headers "dune/*.hh")
-  set_property(GLOBAL PROPERTY headercheck_list ${src_headers} ${dune_headers})
+  # strip hidden files
+  string(REGEX REPLACE "[^;]*/\\.[^;]*\\.hh;?" "" headers "${dune_headers};${src_headers}")
+  set_property(GLOBAL PROPERTY headercheck_list ${headers})
 
   #define headercheck target
   dune_common_script_dir(SCRIPT_DIR)
@@ -66,4 +68,4 @@ macro(finalize_headercheck)
     set_property(TARGET headercheck_${targname} PROPERTY ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/headercheck/${relpath}")
     add_dune_all_flags(headercheck_${targname})
   endforeach(header ${headerlist})
-endmacro(finalize_headercheck)
\ No newline at end of file
+endmacro(finalize_headercheck)