Issue #130: Fixed support for indenting by tab
Allow indent a block of code by selecting a range of lines
and pressing 'tab'. The behavior implemented is the same as
the one in Sublime Text editor since I found it intuitive enough.
/* XPM */
static char *mac_up_xpm[] = {
/* width height ncolors chars_per_pixel */
"14 14 5 1",
/* colors */
"a c white",
"b c #aaaaaa",
"c c #cccccc",
"d c #333366",
"e c #666666",
/* pixels */
"aaaaaaaaaaaaae",
"acccccccccccce",
"acccccddccccce",
"accccdbbdcccce",
"acccdbbbbdccce",
"accdbbbbbbdcce",
"acdbbbbbbbbdce",
"addddbbbbdddde",
"acccdbbbbdccce",
"acccdbbbbdccce",
"acccdbbbbdccce",
"acccddddddccce",
"acccccccccccce",
"eeeeeeeeeeeeee",
};