Bump curve25519 version to 0.5.0

Reflects signalapp/libsignal-protocol-java@3c1a8ee

Also bump Google.Protobuf version to 3.12.4

Author: golf1052

libsignal-protocol-dotnet-tests/libsignal-protocol-dotnet-tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.0</TargetFramework>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
 
     <IsPackable>false</IsPackable>
   </PropertyGroup>

libsignal-protocol-dotnet/libsignal-protocol-dotnet.csproj

@@ -3,23 +3,28 @@
   <PropertyGroup>
     <TargetFramework>netstandard1.4</TargetFramework>
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
-    <IncludeSource>True</IncludeSource>
-    <IncludeSymbols>True</IncludeSymbols>
     <Version>2.7.0</Version>
     <Authors>golf1052, langboost, Trolldemorted</Authors>
     <PackageRequireLicenseAcceptance>True</PackageRequireLicenseAcceptance>
-    <PackageLicenseUrl>https://www.gnu.org/licenses/gpl-3.0.html</PackageLicenseUrl>
+    <PackageLicenseExpression>GPL-3.0-only</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/signal-csharp/libsignal-protocol-dotnet</PackageProjectUrl>
-    <Description>An unofficial .NETStandard signal protocol library</Description>
+    <Description>An unofficial .NET Standard Signal Protocol library based on https://github.com/signalapp/libsignal-protocol-java</Description>
     <RepositoryUrl>https://github.com/signal-csharp/libsignal-protocol-dotnet</RepositoryUrl>
+    <RepositoryType>git</RepositoryType>
     <PackageTags>signal libsignal libsignal-protocol libsignal-protocol-dotnet</PackageTags>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <IncludeSymbols>true</IncludeSymbols>
+    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
+  </PropertyGroup>
+
   <ItemGroup>
-    <PackageReference Include="curve25519-dotnet" Version="1.3.2" />
-    <PackageReference Include="Google.Protobuf" Version="3.5.1" />
+    <PackageReference Include="curve25519-dotnet" Version="0.5.0" />
+    <!-- Do not upgrade! 3.12.4 is the last version to not include System.Memory (Span) which does not work on Windows 10 Mobile. -->
+    <PackageReference Include="Google.Protobuf" Version="3.12.4" />
     <PackageReference Include="May-dotnet" Version="1.2.3" />
     <PackageReference Include="System.Security.Cryptography.Algorithms" Version="4.3.1" />
   </ItemGroup>
 
-</Project>
+</Project>