fix warning: pcf.c
fix warning: limit_inner()
fix warning: vtermlow.c, __tvterm_refresh()
fix warning: swap_int()
fix warning: term.c
fix warning: fbcommon.c, swap_int()
fix warning: fbcommon.c, ptrdiff_t
fix warning: fbdpsp.c
fix: term.c, feature_test_macros
fix warning: vterm.c, delete unused variable
fix: term.c, delete feature_test_macros