contrib: force unicode charset build flag in portaudio vcxproj

Change-Id: I2672a4eb868183b84620bc46d814cf48870707fc

contrib/src/portaudio/pa-vs2017.patch

@@ -24,28 +24,28 @@
 +  <PropertyGroup Label="Globals">
 +    <ProjectGuid>{0A18A071-125E-442F-AFF7-A3F68ABECF99}</ProjectGuid>
 +    <RootNamespace>portaudio</RootNamespace>
-+    <WindowsTargetPlatformVersion>10.0.16299.0</WindowsTargetPlatformVersion>
++    <WindowsTargetPlatformVersion>$(LatestTargetPlatformVersion)</WindowsTargetPlatformVersion>
 +  </PropertyGroup>
 +  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
 +  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
 +    <ConfigurationType>StaticLibrary</ConfigurationType>
-+    <PlatformToolset>v141</PlatformToolset>
-+    <UseOfMfc>false</UseOfMfc>
++    <PlatformToolset>$(DefaultPlatformToolset)</PlatformToolset>
++    <UseOfMfc>false</UseOfMfc><CharacterSet>Unicode</CharacterSet>
 +  </PropertyGroup>
 +  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
 +    <ConfigurationType>StaticLibrary</ConfigurationType>
-+    <PlatformToolset>v141</PlatformToolset>
-+    <UseOfMfc>false</UseOfMfc>
++    <PlatformToolset>$(DefaultPlatformToolset)</PlatformToolset>
++    <UseOfMfc>false</UseOfMfc><CharacterSet>Unicode</CharacterSet>
 +  </PropertyGroup>
 +  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
 +    <ConfigurationType>StaticLibrary</ConfigurationType>
-+    <PlatformToolset>v141</PlatformToolset>
-+    <UseOfMfc>false</UseOfMfc>
++    <PlatformToolset>$(DefaultPlatformToolset)</PlatformToolset>
++    <UseOfMfc>false</UseOfMfc><CharacterSet>Unicode</CharacterSet>
 +  </PropertyGroup>
 +  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
 +    <ConfigurationType>StaticLibrary</ConfigurationType>
-+    <PlatformToolset>v141</PlatformToolset>
-+    <UseOfMfc>false</UseOfMfc>
++    <PlatformToolset>$(DefaultPlatformToolset)</PlatformToolset>
++    <UseOfMfc>false</UseOfMfc><CharacterSet>Unicode</CharacterSet>
 +  </PropertyGroup>
 +  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
 +  <ImportGroup Label="ExtensionSettings">