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 *CheckOn14Win_xpm[] = {
/* width height ncolors chars_per_pixel */
"13 13 4 1",
/* colors */
"a c white",
"b c black",
"c c #808080",
"d c #C0C0C0",
/* pixels */
"cccccccccccca",
"cbbbbbbbbbbda",
"cbaaaaaaaaada",
"cbaaaaaaabada",
"cbaaaaaabbada",
"cbabaaabbbada",
"cbabbabbbaada",
"cbabbbbbaaada",
"cbaabbbaaaada",
"cbaaabaaaaada",
"cbaaaaaaaaada",
"cddddddddddda",
"aaaaaaaaaaaaa",
};