First empty program

Does absolutely nothing useful.

Signed-off-by: Celelibi <celelibi@gmail.com>
misc: Added a module to put misc. functions

It currently have only one function that calls perror and exit.
Certainly more functions to come...

Signed-off-by: Celelibi <celelibi@gmail.com>
misc: added functions asprintf and avsprintf

These functions act like sprintf and vsprintf, except they allocate
their arguments instead of requiring a pre-allocated one.

Signed-off-by: Celelibi <celelibi@gmail.com>
getopthelp: added module getopthelp

This module is a wrapper around getopt_long that handle the short and
long options in an unified way. It can also generate help message
automatically.

Signed-off-by: Celelibi <celelibi@gmail.com>
Makefile: Added generation of .d files

These files contains the dependancies between the .o, .c and .h.

Signed-off-by: Celelibi <celelibi@gmail.com>
getopthelp: Fix comments

Consistent comment-block style. Make valid sentences.

Signed-off-by: Celelibi <celelibi@gmail.com>
getopthelp: Added argidx field

This field is set to the first non-option argument index in argv. So
that the caller can reach its mandatory arguments. It is equivalent to
optind for getopt.

Signed-off-by: Celelibi <celelibi@gmail.com>
filtered_string: Module for accessing strings

It allows the caller to access only the characters that belong to a
given charset without having to modify the real string.

Signed-off-by: Celelibi <celelibi@gmail.com>
filtered_string: Comment fix

Made the comment for function fs_update more explicit.

Signed-off-by: Celelibi <celelibi@gmail.com>
misc: Added function custom_error

This function prints a message on stderr and exit.

Signed-off-by: Celelibi <celelibi@gmail.com>
filtered_string: Don't mark the string as const

Sometimes we need to access it through the struct to modify the data.
Especially in the forthcoming vigenere module.

Signed-off-by: Celelibi <celelibi@gmail.com>
getopthelp: Added argval to the struct state

This field contains the value of the option when it takes one.

Signed-off-by: Celelibi <celelibi@gmail.com>