Date formats

        Two date formats are allowed for dates arguments (-d , -m) :
        - the same than in the logfile
        - relative from now prefixing the argument with '#-' and given a unit
                - y : year
                - M : Month
                - d : day
                - h : hour
                - m : min
                - s : sec

Now an error is triggered if date-min > date-max
Bugfix on date-max searching (on multiple loglines with a date == date-max)

Deleted old argument struct tm* from search function (now using infos
stored in ttail_t.session )

add a -h --help option, deleted -l --logfile options
+ spliting the ttail_search_closest() & ttail_search_print_res() functions

Now we have a running minimal ttail :
src/ttail -d "Mar 6 00:29" -f '%B%n%d %H:%M' -l tests/samples/1.log -l tests/samples/1.1.log

Enhancement in comparison behavior + print function

untested

Set some function inlune and implement an utility function
for file searching functions.

Telling if the logfile array is sorted

ttail_set_flag_re_ex() and ttail_set_flag_re_ci()

For extended & case insensitive regex

Now we can specify a constant length to cut

The getline wrapper will allow to use getline without calling malloc
and free all the time