set c++ version

spec/datatypes.md

@@ -63,6 +63,9 @@ struct LibraryConfig {
 
     /// Include directories
     Array<string> include_dirs;
+
+    /// Optional list of properties
+    Array<Property> properties;
 };
 ```
 
@@ -97,6 +100,9 @@ struct ExecutableConfig {
 
     /// Include directories
     Array<string> include_dirs;
+
+    /// Optional list of properties
+    Array<Property> properties;
 };
 ```
 
@@ -176,4 +182,15 @@ struct TaskConfig {
     /// Shell script to be executed when this task is called
     string shell_script;
 };
+```
+
+## Property
+```c++
+struct Property {
+    /// Property name
+    std::string name;
+
+    /// Property value
+    std::string value;
+};
 ```

spec/functions.md

@@ -89,4 +89,13 @@ Create a task and add it to the build script
 Check if the given option was set on the command line
 
 ## [X] grbc_get_option(option_name: String) -> String
-Get the value of an option
+Get the value of an option
+
+## [X] grbc_property(name: String, value: String) -> Property
+Create a property
+
+## [X] grbc_cxx_version(version_string: String) -> Property
+Create a property that sets the C++ version
+
+## [X] grbc_global_properties(properties: Array<Property>) -> Void
+Set the global property list