Remove unnecessary checks for thread_plan_sp (we check for this at the top of the function.)


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@191476 91177308-0d34-0410-b5e6-96231b3b80d8
DWARF says line number 0 is a valid line number - used to indicate a source line that should 
not have breakpoints set on it inserted into code that does have a valid line number.  So allow
that line number, and the ThreadPlanStepRange should just continue stepping over 0 line ranges
as if they had the same line number as whatever we were previously stepping through.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@191477 91177308-0d34-0410-b5e6-96231b3b80d8
Factor the code that was eliminating redundant breakpoint locations and moving
line breakpoints past the prologue of functions so it can be shared between the
file & line breakpoint resolver, and the source pattern breakpoint resolver,
and then share it.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@191478 91177308-0d34-0410-b5e6-96231b3b80d8