Remove long handling in LuaDouble.toString

The conversion between longs and doubles is a bit confusing. For
instance, consider:

  double x = 900000000000001020d;
  long y = (double) x; // 900000000000001024
  assert x == y; // Is true!

This means that even if (long) x == x, it's not necessarily true that
Long.toString((long)x) == Double.toString(x)! So let's just delete this
special handling, and always use the double formatting code.

src/main/java/org/squiddev/cobalt/LuaDouble.java

@@ -126,24 +126,20 @@ public boolean equals(Object o) {
 
 	@Override
 	public String toString() {
-		long l = (long) v;
-		if (l == v) return Long.toString(l);
 		if (Double.isNaN(v)) return JSTR_NAN;
 		if (Double.isInfinite(v)) return v < 0 ? JSTR_NEGINF : JSTR_POSINF;
 
-		Buffer buffer = new Buffer(4);
+		Buffer buffer = new Buffer(16);
 		NUMBER_FORMAT.format(buffer, v);
 		return buffer.toString();
 	}
 
 	@Override
 	public LuaString checkLuaString() {
-		long l = (long) v;
-		if (l == v) return ValueFactory.valueOf(Long.toString(l));
 		if (Double.isNaN(v)) return STR_NAN;
 		if (Double.isInfinite(v)) return v < 0 ? STR_NEGINF : STR_POSINF;
 
-		Buffer buffer = new Buffer(4);
+		Buffer buffer = new Buffer(16);
 		NUMBER_FORMAT.format(buffer, v);
 		return buffer.toLuaString();
 	}

src/test/resources/spec/base_spec.lua

@@ -50,9 +50,16 @@ describe("The base library", function()
 				expect(tostring(-32767)):eq("-32767")
 			end)
 
-			it("integers :lua>=5.3", function()
+			it("large numbers :lua<=5.2", function()
+				expect(tostring(4611686018427387904)):eq("4.6116860184274e+18")
+				expect(tostring(-4611686018427387904)):eq("-4.6116860184274e+18")
+				expect(tostring(9223372036854775807)):eq("9.2233720368548e+18")
+			end)
+
+			it("integers :lua>=5.3 :!cobalt", function()
 				expect(tostring(4611686018427387904)):eq("4611686018427387904")
 				expect(tostring(-4611686018427387904)):eq("-4611686018427387904")
+				expect(tostring(9223372036854775807)):eq("9223372036854775807")
 			end)
 
 			it("integer-compatible floats are preserved :lua>=5.3 :!cobalt", function()