<rdar://problem/11016907>

Get function boundaries from the LC_FUNCTION_STARTS load command. This helps to determine symbol sizes and also allows us to be able to debug stripped binaries.

If you have a stack backtrace that goes through a function that has been stripped from the symbol table, the variables for any functions above that stack frame will most likely be incorrect. It can also affect our ability to step in/out/through of a function.

llvm-svn: 152381