Get rid of unsightly hex numbers from unified build object files

Get rid of unsightly hex numbers from unified build object files
https://bugs.webkit.org/show_bug.cgi?id=179410

Reviewed by Saam Barati.

Source/JavaScriptCore:

* JavaScriptCore.xcodeproj/project.pbxproj: Rename UnifiedSource*.mm to UnifiedSource*-mm.mm for more readable build output.

Source/WebCore:

* WebCore.xcodeproj/project.pbxproj: Rename UnifiedSource*.mm to UnifiedSource*-mm.mm for more readable build output.

Source/WTF:

* Scripts/generate-unified-source-bundles.rb: For extensions other than "cpp", also include
the extension in the base name of the file, to avoid ugly Xcode-generated object file names.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@224565 268f45cc-cd09-0410-ab3c-d52691b4dbfc