remove nearly-duplicate PATHs in several places

function                                             old     new   delta
bb_PATH_root_path                                      -      35     +35
varunset                                              60      58      -2
arith                                               2042    2033      -9
bb_default_root_login_path                            30       -     -30
.rodata                                           128794  128762     -32
which_main                                           152     117     -35
defpathvar                                            40       -     -40
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(add/remove: 1/2 grow/shrink: 0/4 up/down: 35/-148)          Total: -113 bytes

7 files changed