fold: unicode support. Based on a patch by Tomas Heinrich <heinrich.tomas@gmail.com>

fold: unicode support. Based on a patch by Tomas Heinrich <heinrich.tomas@gmail.com>

General Unicode support is tweaked to expose unicode_status.

function                                             old     new   delta
init_unicode                                           -      77     +77
write2stdout                                           -      19     +19
adjust_column                                         68      71      +3
unicode_status                                         -       1      +1
unicode_is_enabled                                     1       -      -1
grep_main                                            780     773      -7
fold_main                                            619     552     -67
check_unicode_in_env                                  77       -     -77
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(add/remove: 3/2 grow/shrink: 1/2 up/down: 100/-152)          Total: -52 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>