Pass --width to hledger when ledger-report-auto-width is t

[DamienCassou]

I tried to make ledger-mode pass --width for hledger instead of --columns when ledger-report-auto-width is non-nil. I failed because of the way ledger-mode passes arguments to ledger/hledger:

• ledger-mode passes the --columns arguments right after the binary name: i.e., ledger --columns 80 ...
• hledger expects the corresponding --width argument after the register command: i.e., hledger register --width 80 ...

I don't know how to make that work without significantly rewriting this part of ledger-mode. Relevant functions include: ledger-report--compute-extra-args, ledger-report-expand-format-specifiers and ledger-report-binary-format-specifier.

[simonmichael]

Related to #319.