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 *ScrollUp_disabled.xp_xpm[] = {
/* width height ncolors chars_per_pixel */
"15 15 10 1",
/* colors */
"a c #EEEEEE",
"b c #F1F1F1",
"c c #FBFBFB",
"d c #F4F4F4",
"e c #F7F7F7",
"f c #D5D5D5",
"g c #F6F6F6",
"h c #EFEFEF",
"i c #F2F2F2",
"j c none",
/* pixels */
"ccccccccccccccc",
"cediihhhhhhhagc",
"cdiiiihhhhhhhhc",
"ciiiiiihhhhhhhc",
"ciiiihhfhhhhhhc",
"cbiihhfffhhhhhc",
"chihhfffffhhhhc",
"chhhfffhfffhhhc",
"chhfffhhhfffhhc",
"chhhfhhhhhfhhhc",
"cahhhhhhhhhhhhc",
"cahhhhhhhhhhhhc",
"cahhhhhhhhhhhhc",
"cghhhhhhhhhhhgc",
"ccccccccccccccc",
};