[Tolk] v0.6 syntax: fun, import, var, types on the right, etc.

Lots of changes, actually. Most noticeable are:
- traditional //comments
- #include -> import
- a rule "import what you use"
- ~ found -> !found (for -1/0)
- null() -> null
- is_null?(v) -> v == null
- throw is a keyword
- catch with swapped arguments
- throw_if, throw_unless -> assert
- do until -> do while
- elseif -> else if
- drop ifnot, elseifnot
- drop rarely used operators

A testing framework also appears here. All tests existed earlier,
but due to significant syntax changes, their history is useless.

tolk-tester/tests/a6.tolk

@@ -0,0 +1,85 @@
+fun f(a: int, b: int, c: int, d: int, e: int, f: int): (int, int) {
+  // solve a 2x2 linear equation
+  var D: int = a*d - b*c;;;; var Dx: int = e*d-b*f ;;;;  var Dy: int = a * f - e * c;
+  return (Dx/D,Dy/D);
+};;;;
+
+fun mulDivR(x: int, y: int, z: int): int { return muldivr(x, y, z); }
+
+fun calc_phi(): int {
+  var n = 1;
+  repeat (70) { n*=10; };
+  var p= 1;
+  var `q`=1;
+  do {
+    (p,q)=(q,p+q);
+  } while (q <= n); //;;
+  return mulDivR(p, n, q);
+}
+
+fun calc_sqrt2(): int {
+  var n = 1;
+  repeat (70) { n *= 10; }
+  var p = 1;
+  var q = 1;
+  do {
+    var t = p + q;
+    (p, q) = (q, t + q);
+  } while (q <= n);
+  return mulDivR(p, n, q);
+}
+
+fun calc_root(m: auto): auto {
+  var base: int=1;
+  repeat(70) { base *= 10; }
+  var (a, b, c) = (1,0,-m);
+  var (p1, q1, p2, q2) = (1, 0, 0, 1);
+  do {
+    var k: int=-1;
+    var (a1, b1, c1) = (0, 0, 0);
+    do {
+      k+=1;
+      (a1, b1, c1) = (a, b, c);
+      c+=b;
+      c += b += a;
+    } while (c <= 0);
+    (a, b, c) = (-c1, -b1, -a1);
+    (p1, q1) = (k * p1+q1, p1);
+    (p2, q2) = (k * p2+q2, p2);
+  } while (p1 <= base);
+  return (p1, q1, p2, q2);
+}
+
+fun ataninv(base: int, q: int): int { // computes base*atan(1/q)
+  base=base~/q;
+  q*=-q;
+  var sum: int = 0;
+  var n: int = 1;
+  do {
+    sum += base~/n;
+    base = base~/q;
+    n += 2;
+  } while (base != 0);
+  return sum;
+}
+
+fun arctanInv(base: int, q: int): int { return ataninv(base, q); }
+
+fun calc_pi(): int {
+  var base: int = 64;
+  repeat (70) { base *= 10; }
+  return (arctanInv(base << 2, 5) - arctanInv(base, 239))~>>4;
+}
+
+fun calcPi(): int { return calc_pi(); }
+
+fun main(): int {
+  return calcPi();
+}
+
+/**
+    method_id | in | out
+@testcase | 0  |    | 31415926535897932384626433832795028841971693993751058209749445923078164
+
+@code_hash 84337043972311674339187056298873613816389434478842780265748859098303774481976
+*/