Revert "Consistently define DEBUG in debug configs"

This reverts commit 0cab36c319d370744d9d0b2d1446202141e296db.
This change makes MonoDevelop unusable on windows, so rather
than commenting out every Debug.Assert the simplest thing to do
is to just revert this change so we don't have Debug.Assert calls
throwing up modal dialogs all the time.

Conflicts:
	main/src/addins/AspNet/MonoDevelop.AspNet/MonoDevelop.AspNet.csproj
	main/src/addins/CBinding/CBinding.Autotools/CBinding.Autotools.csproj
	main/src/addins/CBinding/CBinding.csproj
	main/src/addins/CSharpBinding/Autotools/Autotools.csproj
	main/src/addins/ChangeLogAddIn/ChangeLogAddIn.csproj
	main/src/addins/Deployment/MonoDevelop.Deployment.Linux/MonoDevelop.Deployment.Linux.csproj
	main/src/addins/Deployment/MonoDevelop.Deployment/MonoDevelop.Deployment.csproj
	main/src/addins/GnomePlatform/GnomePlatform.csproj
	main/src/addins/ILAsmBinding/ILAsmBinding.csproj
	main/src/addins/MonoDevelop.Autotools/MonoDevelop.Autotools.csproj
	main/src/addins/MonoDevelop.DesignerSupport/MonoDevelop.DesignerSupport.csproj
	main/src/addins/MonoDevelop.Gettext/MonoDevelop.Gettext.csproj
	main/src/addins/MonoDevelop.GtkCore/MonoDevelop.GtkCore.csproj
	main/src/addins/MonoDevelop.RegexToolkit/MonoDevelop.RegexToolkit.csproj
	main/src/addins/MonoDevelop.SourceEditor2/MonoDevelop.SourceEditor.csproj
	main/src/addins/MonoDevelop.XmlEditor/MonoDevelop.XmlEditor.csproj
	main/src/addins/MonoDeveloperExtensions/MonoDeveloperExtensions.csproj
	main/src/addins/MonoDeveloperExtensions/NUnit/NUnit.csproj
	main/src/addins/NUnit/MonoDevelop.NUnit.csproj
	main/src/addins/VBNetBinding/VBNetBinding.csproj
	main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion/MonoDevelop.VersionControl.Subversion.csproj
	main/src/addins/VersionControl/MonoDevelop.VersionControl/MonoDevelop.VersionControl.csproj
	main/src/core/Mono.Texteditor/Mono.TextEditor.csproj