Match elseif as a control flow keyword

Syntaxes/CMake Listfile.tmLanguage

@@ -60,7 +60,7 @@
 			<string>(?ix)
 			^\s*	# Start of the line with optional preceding space
 			(?:	# Either a control flow keyword
-				((?:end)?(?:if|while|foreach)|return|else)
+				((?:end)?(?:(?:else)?if|while|foreach)|return|else)
 				|	# Or a function
 				(s(tring|ite_name|ource_group|ubdir(s|_depends)|e(t(_(source_files_properties|t(ests_properties|arget_properties)|directory_properties|property))?|parate_arguments))|c(onfigure_file|reate_test_sourcelist|make(_(policy|minimum_required)| version 2.8.7))|t(arget_link_libraries|ry_(compile|run))|i(n(stall(_(targets|programs|files))?|clude(_(directories|external_msproject|regular_expression))?)|f)|o(utput_required_files|ption)|define_property|u(se_mangled_mesa|nset|tility_source)|project|e(n(d(if|f(oreach|unction)|while|macro)|able_(testing|language))|lse(if)?|x(port(_library_dependencies)?|ec(_program|ute_process)))|variable_(watch|requires)|qt_wrap_(cpp|ui)|f(i(nd_(p(a(ckage|th)|rogram)|file|library)|le)|oreach|unction|ltk_wrap_ui)|w(hile|rite_file)|l(i(st|nk_(directories|libraries))|oad_c(ommand|ache))|a(dd_(subdirectory|custom_(command|target)|test|de(pendencies|finitions)|executable|library)|ux_source_directory)|re(turn|move(_definitions)?)|get_(source_file_property|cmake_property|t(est_property|arget_property)|directory_property|property|filename_component)|m(essage|a(cro|th|ke_directory|rk_as_advanced))|b(uild_(name|command)|reak))
 				|	# Or some function we don’t know about