column: make more obvious what is default behavior

column: make more obvious what is default behavior

The man page contains mistakes. The default is to fill columns before
lines:

$ printf 'aaaaaaaaaaaaaaaaaaaaaa\nBBBBBBBBBBBBBBBBBBBBB\nXXXXXXX\nYYYYYYYYYYY\nZZZZZ' > data

$ column --columns 80 < data
aaaaaaaaaaaaaaaaaaaaaa	XXXXXXX			ZZZZZ
BBBBBBBBBBBBBBBBBBBBB	YYYYYYYYYYY

$ column  --fillrows --columns 80 < data
aaaaaaaaaaaaaaaaaaaaaa	BBBBBBBBBBBBBBBBBBBBB	XXXXXXX
YYYYYYYYYYY		ZZZZZ

The patch also rename functions in the code to make it more obvious
for code readers.

Signed-off-by: Karel Zak <kzak@redhat.com>