Try to split long lines on spaces

Try to split long lines on spaces to avoid words being splitted. This
can be turned off with the option `split_line_on_space'. The code
assumes that the terminal encoding has ASCII spaces.

src/core/misc.h

@@ -116,6 +116,6 @@ uoff_t str_to_uofft(const char *str);
 int find_substr(const char *list, const char *item);
 
 /* split `str' into `len' sized substrings */
-char **strsplit_len(const char *str, int len);
+char **strsplit_len(const char *str, int len, gboolean onspace);
 
 #endif