Add behavior of conversion to integral type

Author: mborland

doc/modules/ROOT/pages/decimal32_t.adoc

@@ -164,3 +164,23 @@ Constructs a decimal value that matches `str` subject to:
 . On overflow constructs `INF`
 . On underflow constructs `0`
 . Rounds value represented by `str` according to current rounding mode
+
+=== Conversion to integral type
+
+[source,c++]
+----
+// 3.2.2.4 Conversion to integral type
+
+explicit constexpr operator int() const noexcept;
+explicit constexpr operator unsigned() const noexcept;
+explicit constexpr operator long() const noexcept;
+explicit constexpr operator unsigned long() const noexcept;
+explicit constexpr operator long long() const noexcept;
+explicit constexpr operator unsigned long long() const noexcept;
+----
+
+Constructs an integer representation of the decimal value subject to:
+
+. If the decimal value is `INF` returns `std::numeric_limits<IntegerType>::max()`
+. If the decimal value is `NAN` returns `std::numeric_limits<IntegerType>::max()`
+. If the decimal value exceeds the range of the `IntegerType` returns `std::numeric_limits<IntegerType>::max()`