Fix Clang warning regarding null pointer argument.

This warning was showing up in the Clang static analyzer in Xcode: "Null pointer argument in call to memory copy function"

Fix provided by Ian Wilkinson.
Review URL: https://breakpad.appspot.com/569002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1162 4c0a9323-5329-0410-9bdc-e9ce6186880e
Add an option to not handle DWARF inter-compilation unit references in Linux dump_syms. 

This saves a lot of memory for dump_syms.

Review URL: https://breakpad.appspot.com/565002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1163 4c0a9323-5329-0410-9bdc-e9ce6186880e
Cleanup: Use scoped_ptr where appropriate in DwarfCUToModule.

Review URL: https://breakpad.appspot.com/572002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1164 4c0a9323-5329-0410-9bdc-e9ce6186880e