Improve comparison predicate logic (#163)

Replace existing Value.cmp(), with the full rules layed out by
ISO/IEC 9075-2:2016(E), 8.2, <comparison predicate>

SQL Standard E011-06

docs/sql-compliance.rst

@@ -13,7 +13,7 @@ Mandatory Features
 ------------------
 
 As of the latest version (or at least the version of this documentation)
-**vsql supports 59 of the 164 mandatory features** of the
+**vsql supports 60 of the 164 mandatory features** of the
 `SQL:2016 Standard <https://www.iso.org/standard/63556.html>`_.
 
 .. list-table:: Table 43 — Feature taxonomy and definition for mandatory features
@@ -40,7 +40,7 @@ As of the latest version (or at least the version of this documentation)
    * - ✅ E011-05
      - Numeric comparison
 
-   * - ❌ E011-06
+   * - ✅ E011-06
      - Implicit casting among the numeric data types
 
    * - ⭕ **E021**

tests/bigint.sql

@@ -104,13 +104,13 @@ VALUES CAST(123 AS BIGINT) / 53.7;
 -- COL1: 2
 
 VALUES -123.7 / CAST(53 AS BIGINT);
--- COL1: -3
+-- COL1: -2
 
 VALUES CAST(-5000000000000000000 AS BIGINT) / 0.02;
 -- error 22012: division by zero
 
 VALUES -5000000000000000000.7 / CAST(3.2 AS BIGINT);
--- COL1: -1666666666666666667
+-- COL1: -1666666666666666666
 
 VALUES CAST(-5000000000000000000 AS BIGINT) / 0;
 -- error 22012: division by zero