Add pow1p to the docs

Author: mborland

Diff for: doc/math.qbk

@@ -313,6 +313,7 @@ and use the function's name as the link text.]
 [def __sqrt1pm1 [link math_toolkit.powers.sqrt1pm1 sqrt1pm1]]
 [def __rsqrt [link math_toolkit.powers.rsqrt rsqrt]]
 [def __powm1 [link math_toolkit.powers.powm1 powm1]]
+[def __pow1p [link math_toolkit.powers.pow1p pow1p]]
 [def __hypot [link math_toolkit.powers.hypot hypot]]
 [def __pow [link math_toolkit.powers.ct_pow pow]]
 

Diff for: doc/sf/pow1p.qbk

@@ -0,0 +1,34 @@
+[/
+  Copyright Matt Borland 2024
+  Distributed under the Boost Software License, Version 1.0.
+  (See accompanying file LICENSE_1_0.txt or copy at
+  http://www.boost.org/LICENSE_1_0.txt).
+]
+
+[section:pow1p pow1p]
+
+[h4 Synopsis]
+
+    #include <boost/math/special_functions/pow1p.hpp>
+
+    namespace boost {
+    namespace math {
+
+    template <typename T1, typename T2, typename Policy>
+    BOOST_MATH_GPU_ENABLED tools::promote_args_t<T1, T2>
+    pow1p(const T1 x, const T2 y, const Policy& pol)
+
+    template <typename T1, typename T2>
+    BOOST_MATH_GPU_ENABLED tools::promote_args_t<T1, T2>
+    pow1p(const T1 x, const T2 y)
+
+    }} // namespaces
+
+
+The function `pow1p` computes (1 + x)[super y ] where x and y are real numbers. 
+This function is particularly useful for scenarios where adding 1 to x before raising it to the power of y is required. 
+It provides a more numerically stable and efficient way to perform this computation, especially for small values of x.
+When x is very small, directly computing (1 + x)[super y ] using standard arithmetic operations can lead to a loss of precision due to floating-point arithmetic limitations. 
+The pow1p function helps mitigate this issue by internally handling such cases more accurately.
+
+[endsect]