Keep original source path and mapped path in LineEntry

Summary:
The "file" variable in a LineEntry was mapped using target.source-map, except when stepping through inlined code. This patch adds a new variable to LineEntry, "original_file", that contains the original file from the debug info. "file" will continue to (possibly) be mapped.

Some code has been changed to use "original_file". This is code dealing with symbols. Code dealing with source files will still use "file". Reviewers, please confirm that these particular changes are correct.

Tests run on Ubuntu 12.04 show no regression.

Reviewers: clayborg, jingham

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D20135

llvm-svn: 269250