BUG: Fix mistranslated expression in amos.h

Closes gh-46.

Thanks to github user hchau630 for identifying the problem
and suggesting the fix.

Author: WarrenWeckesser

include/xsf/amos/amos.h

@@ -4132,7 +4132,7 @@ namespace amos {
                 continue;
             }
             cs = -zr + std::log(s1);
-            cs = (exp(std::real(cs)) / tol) * (cos(std::imag(cs)) + sin(std::imag(cs) * std::complex<double>(0, 1)));
+            cs = (exp(std::real(cs)) / tol) * std::complex<double>(cos(std::imag(cs)), sin(std::imag(cs)));
             if (!uchk(cs, *ascle, tol)) {
                 y[i - 1] = cs;
                 nz -= 1;