optimize column width calculation and utf-8 encode for ASCII

In particular on OpenBSD and on glibc wcwidth() is quite expensive.
On musl there is little difference.

diff --git a/st.c b/st.c
index 5d4054f..1414f98 100644 (file)
--- a/st.c
+++ b/st.c
@@ -2307,7 +2307,7 @@ tputc(Rune u)
        Glyph *gp;
 
        control = ISCONTROL(u);
-       if (!IS_SET(MODE_UTF8 | MODE_SIXEL)) {
+       if (u < 127 || !IS_SET(MODE_UTF8 | MODE_SIXEL)) {
                c[0] = u;
                width = len = 1;
        } else {