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.
#define ScrollDn_width 8
#define ScrollDn_height 8
static unsigned char ScrollDn_bits[] = {
0x00, 0x7e, 0x7e, 0x3c, 0x3c, 0x18, 0x18, 0x00};