Fix: Base library issues in Int8/16/32/64 (#478)

Fix some issues reported in #476:
* Offer minimum and maximum integer constants
* Remove superfluous second argument in `bitnot()`

src/Int16.mo

@@ -10,6 +10,12 @@ module {
   /// 16-bit signed integers.
   public type Int16 = Prim.Types.Int16;
 
+  /// Minimum 16-bit integer value, `-2 ** 15`.
+  public let minimumValue = -32_768 : Int16;
+
+  /// Maximum 16-bit integer value, `+2 ** 15 - 1`.
+  public let maximumValue = 32_767 : Int16;
+
   /// Converts a 16-bit signed integer to a signed integer with infinite precision.
   ///
   /// Example:
@@ -279,16 +285,14 @@ module {
   public func pow(x : Int16, y : Int16) : Int16 { x ** y };
 
   /// Returns the bitwise negation of `x`, `^x`.
-  /// Issue: The argument `y` is not needed and will be removed in future.
   ///
   /// Example:
   /// ```motoko
   /// import Int16 "mo:base/Int16";
   ///
-  /// let unused = 0 : Int16; // will be fixed in future
-  /// Int16.bitnot(-256 /* 0xff00 */, unused) // => +255 // 0xff
+  /// Int16.bitnot(-256 /* 0xff00 */) // => +255 // 0xff
   /// ```
-  public func bitnot(x : Int16, y : Int16) : Int16 { ^x };
+  public func bitnot(x : Int16) : Int16 { ^x };
 
   /// Returns the bitwise "and" of `x` and `y`, `x & y`.
   ///

src/Int32.mo

@@ -10,6 +10,12 @@ module {
   /// 32-bit signed integers.
   public type Int32 = Prim.Types.Int32;
 
+  /// Minimum 32-bit integer value, `-2 ** 31`.
+  public let minimumValue = -2_147_483_648 : Int32;
+
+  /// Maximum 32-bit integer value, `+2 ** 31 - 1`.
+  public let maximumValue = 2_147_483_647 : Int32;
+
   /// Converts a 32-bit signed integer to a signed integer with infinite precision.
   ///
   /// Example:
@@ -279,16 +285,14 @@ module {
   public func pow(x : Int32, y : Int32) : Int32 { x ** y };
 
   /// Returns the bitwise negation of `x`, `^x`.
-  /// Issue: The argument `y` is not needed and will be removed in future.
   ///
   /// Example:
   /// ```motoko
   /// import Int32 "mo:base/Int32";
   ///
-  /// let unused = 0 : Int32; // will be fixed in future
-  /// Int32.bitnot(-256 /* 0xffff_ff00 */, unused) // => +255 // 0xff
+  /// Int32.bitnot(-256 /* 0xffff_ff00 */) // => +255 // 0xff
   /// ```
-  public func bitnot(x : Int32, y : Int32) : Int32 { ^x };
+  public func bitnot(x : Int32) : Int32 { ^x };
 
   /// Returns the bitwise "and" of `x` and `y`, `x & y`.
   ///

src/Int64.mo

@@ -10,6 +10,12 @@ module {
   /// 64-bit signed integers.
   public type Int64 = Prim.Types.Int64;
 
+  /// Minimum 64-bit integer value, `-2 ** 63`.
+  public let minimumValue = -9_223_372_036_854_775_808 : Int64;
+
+  /// Maximum 64-bit integer value, `+2 ** 63 - 1`.
+  public let maximumValue = 9_223_372_036_854_775_807 : Int64;
+
   /// Converts a 64-bit signed integer to a signed integer with infinite precision.
   ///
   /// Example:
@@ -279,16 +285,14 @@ module {
   public func pow(x : Int64, y : Int64) : Int64 { x ** y };
 
   /// Returns the bitwise negation of `x`, `^x`.
-  /// Issue: The argument `y` is not needed and will be removed in future.
   ///
   /// Example:
   /// ```motoko
   /// import Int64 "mo:base/Int64";
   ///
-  /// let unused = 0 : Int64; // will be fixed in future
-  /// Int64.bitnot(-256 /* 0xffff_ffff_ffff_ff00 */, unused) // => +255 // 0xff
+  /// Int64.bitnot(-256 /* 0xffff_ffff_ffff_ff00 */) // => +255 // 0xff
   /// ```
-  public func bitnot(x : Int64, y : Int64) : Int64 { ^x };
+  public func bitnot(x : Int64) : Int64 { ^x };
 
   /// Returns the bitwise "and" of `x` and `y`, `x & y`.
   ///

src/Int8.mo

@@ -10,6 +10,12 @@ module {
   /// 8-bit signed integers.
   public type Int8 = Prim.Types.Int8;
 
+  /// Minimum 8-bit integer value, `-2 ** 7`.
+  public let minimumValue = -128 : Int8;
+
+  /// Maximum 8-bit integer value, `+2 ** 7 - 1`.
+  public let maximumValue = 127 : Int8;
+
   /// Converts a 8-bit signed integer to a signed integer with infinite precision.
   ///
   /// Example:
@@ -279,16 +285,14 @@ module {
   public func pow(x : Int8, y : Int8) : Int8 { x ** y };
 
   /// Returns the bitwise negation of `x`, `^x`.
-  /// Issue: The argument `y` is not needed and will be removed in future.
   ///
   /// Example:
   /// ```motoko
   /// import Int8 "mo:base/Int8";
   ///
-  /// let unused = 0 : Int8; // will be fixed in future
-  /// Int8.bitnot(-16 /* 0xf0 */, unused) // => +15 // 0x0f
+  /// Int8.bitnot(-16 /* 0xf0 */) // => +15 // 0x0f
   /// ```
-  public func bitnot(x : Int8, y : Int8) : Int8 { ^x };
+  public func bitnot(x : Int8) : Int8 { ^x };
 
   /// Returns the bitwise "and" of `x` and `y`, `x & y`.
   ///