Simpleperf: improve symbol parsing.

Support c++ symbol demangling, and add option to disable it.
Add option to set symfs dir, so it can report on host.
Add label symbols, add add symbol length fixing for it.
Add two hacks about arm elf symbol parsing.

Bug: 19483574

Change-Id: I300d6c007c8634db382d0a50627b9cde1502df89
5 files changed