Update Marshal.PtrToStringAnsi - UTF-8 on Unix (#4238)

* Update Marshal.PtrToStringAnsi - UTF-8 on Unix

* Change mentions of Unicode to UTF-16

Author: nxtn

xml/System.Runtime.InteropServices/Marshal.xml

@@ -6168,7 +6168,7 @@ There is a difference in the behavior of the `GetLastWin32Error` method on .NET
         <AssemblyVersion>4.2.0.0</AssemblyVersion>
       </AssemblyInfo>
       <Docs>
-        <summary>Allocates a managed <see cref="T:System.String" /> and copies all or part of an unmanaged ANSI string into it.</summary>
+        <summary>Allocates a managed <see cref="T:System.String" /> and copies all or part of an unmanaged ANSI (on Windows) or UTF-8 (on Unix) string into it.</summary>
       </Docs>
     </MemberGroup>
     <Member MemberName="PtrToStringAnsi">
@@ -6216,8 +6216,8 @@ There is a difference in the behavior of the `GetLastWin32Error` method on .NET
       </Parameters>
       <Docs>
         <param name="ptr">The address of the first character of the unmanaged string.</param>
-        <summary>Copies all characters up to the first null character from an unmanaged ANSI string to a managed <see cref="T:System.String" />, and widens each ANSI character to Unicode.</summary>
-        <returns>A managed string that holds a copy of the unmanaged ANSI string. If <paramref name="ptr" /> is <see langword="null" />, the method returns a null string.</returns>
+        <summary>Copies all characters up to the first null character from an unmanaged ANSI or UTF-8 string to a managed <see cref="T:System.String" />, and widens each character to UTF-16.</summary>
+        <returns>A managed string that holds a copy of the unmanaged string. If <paramref name="ptr" /> is <see langword="null" />, the method returns a null string.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[  
 
@@ -6284,8 +6284,8 @@ There is a difference in the behavior of the `GetLastWin32Error` method on .NET
       <Docs>
         <param name="ptr">The address of the first character of the unmanaged string.</param>
         <param name="len">The byte count of the input string to copy.</param>
-        <summary>Allocates a managed <see cref="T:System.String" />, copies a specified number of characters from an unmanaged ANSI string into it, and widens each ANSI character to Unicode.</summary>
-        <returns>A managed string that holds a copy of the native ANSI string if the value of the <paramref name="ptr" /> parameter is not <see langword="null" />; otherwise, this method returns <see langword="null" />.</returns>
+        <summary>Allocates a managed <see cref="T:System.String" />, copies a specified number of characters from an unmanaged ANSI or UTF-8 string into it, and widens each character to UTF-16.</summary>
+        <returns>A managed string that holds a copy of the native string if the value of the <paramref name="ptr" /> parameter is not <see langword="null" />; otherwise, this method returns <see langword="null" />.</returns>
         <remarks>
           <format type="text/markdown"><![CDATA[