fix compilation with clang++
Makefile: hide object files
Editor: fix utf8 handling in prepare_insert
Add alt-[kK] for keeping only selections matching/not matching a given regex
use Y for concatenated yank
display a message in the status line when yanking
compile with -pedantic option and fix warnings
do not check buffer invariant in do_{erase,insert} as this cause O(n²) behaviour
Pass a fg and bg color when displaying a menu
pass a color pair when displaying an information window
Add get_color helper function
UserInterface: status line messages are now DisplayLines

This add color support for the status line
InputHandler::prompt takes a color pair to use
Dynamically change prompt color for regex prompt depending on regex validity