[Tolk] Rewrite lexer, spaces are not mandatory anymore

A new lexer is noticeably faster and memory efficient
(although splitting a file to tokens is negligible in a whole pipeline).

But the purpose of rewriting lexer was not just to speed up,
but to allow writing code without spaces:
`2+2` is now 4, not a valid identifier as earlier.

The variety of symbols allowed in identifier has greatly reduced
and is now similar to other languages.

SrcLocation became 8 bytes on stack everywhere.

Command-line flags were also reworked:
- the input for Tolk compiler is only a single file now, it's parsed, and parsing continues while new #include are resolved
- flags like -A -P and so on are no more needed, actually

tolk/CMakeLists.txt

@@ -1,10 +1,9 @@
 cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
 
 set(TOLK_SOURCE
-        srcread.cpp
+        src-file.cpp
         lexer.cpp
         symtable.cpp
-        keywords.cpp
         unify-types.cpp
         parse-tolk.cpp
         abscode.cpp