minor, introduce zeroes, ctl_zero_price(), ctl_zero_quant(), etc.

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, print diagnostic message when no command is specified

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, actually initialise the sum slot of ctx to zero explicitly

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
test, adapt tests to behaviour change introduced in last commit

Now that the sum of corporate action events is explicitly zeroed,
the arithmetic will use as few additional digits as possible, so
existing tests were outright wrong.

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'core/zeroes'

* core/zeroes:
  test, adapt tests to behaviour change introduced in last commit
  minor, actually initialise the sum slot of ctx to zero explicitly
  minor, print diagnostic message when no command is specified
  minor, introduce zeroes, ctl_zero_price(), ctl_zero_quant(), etc.