Removed some hard-coded windows target platform versions

examples/DSP module plugin demo/DSP module plugin demo.jucer

@@ -55,7 +55,7 @@
         <MODULEPATH id="juce_dsp" path="../../modules"/>
       </MODULEPATHS>
     </XCODE_MAC>
-    <VS2015 targetFolder="Builds/VisualStudio2015" windowsTargetPlatformVersion="8.1">
+    <VS2015 targetFolder="Builds/VisualStudio2015">
       <CONFIGURATIONS>
         <CONFIGURATION name="Debug" winWarningLevel="4" generateManifest="1" winArchitecture="x64"
                        isDebug="1" optimisation="1" targetName="DSPModulePluginDemo"

extras/Projucer/Projucer.jucer

@@ -30,7 +30,7 @@
       </MODULEPATHS>
     </XCODE_MAC>
     <VS2013 targetFolder="Builds/VisualStudio2013" externalLibraries="" extraLinkerFlags=""
-            bigIcon="rv1F4h" toolset="v120" vstFolder="" windowsTargetPlatformVersion="8.1">
+            bigIcon="rv1F4h" toolset="v120" vstFolder="">
       <CONFIGURATIONS>
         <CONFIGURATION name="Debug" winWarningLevel="4" generateManifest="1" winArchitecture="x64"
                        isDebug="1" optimisation="1" targetName="Projucer" headerPath=""
@@ -52,7 +52,7 @@
       </MODULEPATHS>
     </VS2013>
     <VS2015 targetFolder="Builds/VisualStudio2015" externalLibraries="" bigIcon="rv1F4h"
-            toolset="v140" vstFolder="" windowsTargetPlatformVersion="8.1">
+            toolset="v140" vstFolder="">
       <CONFIGURATIONS>
         <CONFIGURATION name="Debug" winWarningLevel="4" generateManifest="1" winArchitecture="x64"
                        isDebug="1" optimisation="1" targetName="Projucer" headerPath=""
@@ -73,7 +73,7 @@
         <MODULEPATH id="juce_core" path="../../modules"/>
       </MODULEPATHS>
     </VS2015>
-    <VS2017 targetFolder="Builds/VisualStudio2017" bigIcon="rv1F4h" windowsTargetPlatformVersion="10.0.15063.0">
+    <VS2017 targetFolder="Builds/VisualStudio2017" bigIcon="rv1F4h">
       <CONFIGURATIONS>
         <CONFIGURATION name="Debug" winWarningLevel="4" generateManifest="1" winArchitecture="x64"
                        isDebug="1" optimisation="1" targetName="Projucer" debugInformationFormat="ProgramDatabase"