py/misc: Fix truncating cast to char.

Explicitly specify the wanted cast otherwise this results in

    warning C4244: '=': conversion from 'unichar' to 'char',
    possible loss of data

when building with msvc with most warnings enabled.

Signed-off-by: stijn <stijn@ignitron.net>

Author: stinos

py/misc.h

@@ -243,7 +243,7 @@ static inline void vstr_ins_byte(vstr_t *vstr, size_t byte_pos, byte b) {
 static inline void vstr_ins_char(vstr_t *vstr, size_t char_pos, unichar chr) {
     // TODO UNICODE
     char *s = vstr_ins_blank_bytes(vstr, char_pos, 1);
-    *s = chr;
+    *s = (char)chr;
 }
 static inline void vstr_ins_strn(vstr_t *vstr, size_t byte_pos, const char *str, size_t len) {
     char *s = vstr_ins_blank_bytes(vstr, byte_pos, len);