Untitled Sections Should be Independent

[brodieG]

With input:

b <- 24
unitizer_sect("A", {
  a <- 42
  a + 1
  a + 2
})
unitizer_sect("B", {
  b <- 25
  b + 1
  b + 2
})
unitizer_sect("A", {
  a + 3
})
c <- 7

The resulting unitizer data combines the first and last lines into one section:

Browse[1]> [email protected]
  id    call    section ignored status user reviewed
1  1 b <- 24 <untitled>    TRUE    New    N    FALSE
2  2  c <- 7 <untitled>    TRUE    New    N    FALSE
3  3 a <- 42          A    TRUE    New    N    FALSE
4  4   a + 1          A   FALSE    New    N    FALSE
5  5   a + 2          A   FALSE    New    N    FALSE
6  6 b <- 25          B    TRUE    New    N    FALSE
7  7   b + 1          B   FALSE    New    N    FALSE
8  8   b + 2          B   FALSE    New    N    FALSE
9  9   a + 3        A.1   FALSE    New    N    FALSE

It should make unique sections like with the A sections, otherwise sequencing ends up wrong.

See #278 for location where we dumped the above from.