STYLE: Scripts with shebang should be executable

scripts/eigen_gen_split_test_help.cmake: has a shebang but is not marked executable!
scripts/eigen_gen_docs: has a shebang but is not marked executable!
bench/basicbench.cxxlist: has a shebang but is not marked executable!
ci/scripts/vars.linux.sh: has a shebang but is not marked executable!
ci/scripts/test.linux.after_script.sh: has a shebang but is not marked executable!
ci/scripts/build.linux.script.sh: has a shebang but is not marked executable!
ci/scripts/common.linux.before_script.sh: has a shebang but is not marked executable!
ci/scripts/test.linux.script.sh: has a shebang but is not marked executable!
bench/btl/data/mk_gnuplot_script.sh: has a shebang but is not marked executable!
bench/btl/data/mk_mean_script.sh: has a shebang but is not marked executable!

What does this implement/fix?

Files that start with shebang "#!/bin/programname" should also have execute permissions set.