[Tolk] Embedded stdlib.tolk, CompilerState, strict includes

Several related changes:
- stdlib.tolk is embedded into a distribution (deb package or tolk-js),
  the user won't have to download it and store as a project file;
  it's an important step to maintain correct language versioning
- stdlib.tolk is auto-included, that's why all its functions are
  available out of the box
- strict includes: you can't use symbol `f` from another file
  unless you've #include'd this file
- drop all C++ global variables holding compilation state,
  merge them into a single struct CompilerState located at
  compiler-state.h; for instance, stdlib filename is also there

tolk/abscode.cpp

@@ -15,6 +15,7 @@
     along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
 */
 #include "tolk.h"
+#include "compiler-state.h"
 
 namespace tolk {
 
@@ -59,7 +60,7 @@ void TmpVar::dump(std::ostream& os) const {
 
 void TmpVar::show(std::ostream& os, int omit_idx) const {
   if (cls & _Named) {
-    os << symbols.get_name(name);
+    os << G.symbols.get_name(name);
     if (omit_idx && (omit_idx >= 2 || (cls & _UniqueName))) {
       return;
     }