Reduce memory usage

[cwbaker]

Reduce memory usage by removing vector of symbols from GrammarSymbolSet and only generating labels for Graphviz DOT graphs not when generating parse tables that don't use labels.

[mingodad]

Still missing pthread:

------------------ src/lalr/lalr_examples/lalr_examples.forge ------------------
index 6aed8b3..0328435 100644
@@ -6,20 +6,21 @@ for _, cc in toolsets('^cc.*') do

     local lalr_examples = cc:Executable '${bin}/lalr_examples' {
         '${lib}/lalr_${platform}_${architecture}';
+   libraries = {"pthread"};
         cc:Cxx '${obj}/%1' {
             "lalr_examples.cpp",
             "lalr_error_handling_calculator_example.cpp",
             "lalr_hello_world_example.cpp",
             "lalr_json_example.cpp",
             "lalr_calculator_example.cpp",
-            "lalr_xml_example.cpp"        
+            "lalr_xml_example.cpp"
         };
     };

     -- If the Lalrc target prototype has been defined then use it to rebuild
     -- the example parse tables from grammars.  Otherwise just use the source
     -- files directly.
-    if cc.Lalrc then 
+    if cc.Lalrc then
         lalr_examples {
             cc:Cxx '${obj}/%1' {
                 cc:Lalrc '${obj}/%1.cpp' {

---------------------- src/lalr/lalr_test/lalr_test.forge ----------------------
index ff4e1e4..d2c241e 100644
@@ -4,6 +4,7 @@ for _, cc in toolsets('^cc.*') do
         cc:Executable '${bin}/lalr_test' {
             '${lib}/lalr_${platform}_${architecture}';
             '${lib}/UnitTest++_${platform}_${architecture}';
+       libraries = {"pthread"};

             cc:Cxx '${obj}/%1' {
                 'main.cpp',
-------------------------- src/lalr/lalrc/lalrc.forge --------------------------
index bdab5a3..d2eddd2 100644
@@ -1,8 +1,9 @@

-for _, cc in toolsets('^cc.*') do    
+for _, cc in toolsets('^cc.*') do
     cc:all {
         cc:Executable '${bin}/lalrc' {
             '${lib}/lalr_${platform}_${architecture}';
+       libraries = {"pthread"};
             cc:Cxx '${obj}/%1' {
                 'dot.cpp';
                 'lalrc.cpp';