All symbols starting with 'x' in FreeBSD

• xchg netinet/tcp_subr.c:170
• X_db_line_at_pc ddb/db_aout.c:212
• X_db_lookup ddb/db_aout.c:126
• X_db_search_symbol ddb/db_aout.c:149
• X_db_symbol_values ddb/db_aout.c:197
• X_db_sym_init ddb/db_aout.c:75
• xmit_print i386/isa/if_is.c:998