[serialization] Stop recording the full paths to input source files.

There were no clients and it leaks information about the developer's system.
After this commit, there should be no full paths present in framework modules.
(App modules may contain search paths for debugging reasons, as well as a
full or relative path to the bridging header.)

Swift SVN r24851

include/swift/Serialization/ModuleFile.h

@@ -75,9 +75,6 @@ class ModuleFile : public LazyMemberLoader {
   /// The data blob containing all of the module's identifiers.
   StringRef IdentifierData;
 
-  /// Paths to the source files used to build this module.
-  SmallVector<StringRef, 4> SourcePaths;
-
 public:
   /// Represents another module that has been imported as a dependency.
   class Dependency {
@@ -471,12 +468,6 @@ public:
     return static_cast<ModuleStatus>(Bits.Status);
   }
 
-  /// Returns paths to the source files that were used to build this module.
-  ArrayRef<StringRef> getInputSourcePaths() const {
-    assert(getStatus() == ModuleStatus::Valid);
-    return SourcePaths;
-  }
-
   /// Returns the list of modules this module depends on.
   ArrayRef<Dependency> getDependencies() const {
     return Dependencies;