[DWARF] Add logging to range building

[SingleAccretion]

This helps one gain insight into how and why variable ranges end up as they do. #9900 is an example of an investigation using this code.

Sample output:

Building ranges for values in scope: [0..186)
L#0   : %r13@[49..68)
L#2   : %rbx@[59..68) %rbx@[72..145)
L#5   : %rax@[100..105)
L#8   : %rax@[116..121)
L#11  : %rax@[132..142)
L#12  : %r9@[137..142)
L#13  : %rax@[142..157)
VMCTX : %rdi@[49..100) %r14@[100..157)    
Intersecting with L#2    
Intersecting with VMCTX    
Built ranges:    
[L#2:%rbx, VMCTX:%rdi]@[59..68)    
[L#2:%rbx, VMCTX:%rdi]@[72..100)    
[L#2:%rbx, VMCTX:%r14]@[100..145)    

[alexcrichton]

Thanks!