Merge pull request #2532 from opentable/master

Configuration specific preprocessor definition can generate a lot of warning

lib/cocoapods/generator/target_environment_header.rb

@@ -49,7 +49,7 @@ module Pod
         specs_by_config = specs_scoped_by_configuration(common_specs, specs_by_configuration)
         specs_by_config.each do |config, specs|
           result << "// #{config} build configuration\n"
-          result << "#ifdef #{config.gsub(' ', '_').upcase}\n\n"
+          result << "#ifdef #{config.gsub(/[^a-zA-Z0-9_]/, '_').upcase}\n\n"
           specs.each { |spec| result << spec_defines(spec, 1) }
           result << "#endif\n"
         end