chore: add c implementation for acovercos

Author: adarshpalaskar1

lib/node_modules/@stdlib/math/base/special/acovercos/lib/native.js

@@ -33,20 +33,16 @@ var addon = require( './../src/addon.node' );
 * @returns {number} inverse coversed cosine (in radians)
 *
 * @example
-* var v = acovercos( 3.141592653589793/2.0 );
-* // returns NaN
-*
-* @example
 * var v = acovercos( 0.0 );
 * // returns ~1.5708
 *
 * @example
-* var v = acovercos( 3.141592653589793/6.0 );
-* // returns NaN
+* var v = acovercos( -3.141592653589793/2.0 );
+* // returns ~-0.6075
 *
 * @example
-* var v = acovercos( -1.0 );
-* // returns 0.0
+* var v = acovercos( -3.141592653589793/6.0 );
+* // returns ~0.4966
 *
 * @example
 * var v = acovercos( NaN );