Also allow lcase global keyword

Closes #221

cheatsheet.md

@@ -229,11 +229,13 @@ var k = 5; // initialized to 5 (integer)
 var l := k; // reference to k
 auto &m = k; // reference to k
 
-GLOBAL g = 5; // creates a global variable. If global already exists, it is not re-added
+global g = 5; // creates a global variable. If global already exists, it is not re-added
-GLOBAL g = 2; // global 'g' now equals 2
+global g = 2; // global 'g' now equals 2
 
-GLOBAL g2;
+global g2;
-if (g2.is_var_undef()) { g2 = 4; } // only initialize g2 once, if GLOBAL decl hit more than once
+if (g2.is_var_undef()) { g2 = 4; } // only initialize g2 once, if global decl hit more than once
+
+GLOBAL g3; // all upper case version also accepted
 ```
 
 ## Built in Types

include/chaiscript/language/chaiscript_engine.hpp

@@ -342,6 +342,7 @@ namespace chaiscript
       m_engine.add_reserved_word("class");
       m_engine.add_reserved_word("attr");
       m_engine.add_reserved_word("var");
+      m_engine.add_reserved_word("global");
       m_engine.add_reserved_word("GLOBAL");
       m_engine.add_reserved_word("_");
 

include/chaiscript/language/chaiscript_parser.hpp

@@ -2065,7 +2065,7 @@ namespace chaiscript
           }
 
           build_match<eval::Var_Decl_AST_Node>(prev_stack_top);
-        } else if (Keyword("GLOBAL")) {
+        } else if (Keyword("GLOBAL") || Keyword("global")) {
           retval = true;
 
           if (!(Reference() || Id())) {

unittests/global_lcase.chai

@@ -0,0 +1,18 @@
+// Test global 
+
+global g = 3;
+assert_true(g == 3);
+
+var v := g;
+assert_true(v == 3);
+
+global g = 2;
+assert_true(g == 2);
+assert_true(v == 2);
+
+def f() {
+  assert_true(g == 2);
+}
+
+f();
+