iron out all extra compiler warnings

iron out all extra compiler warnings

gcc 9.1 on x86/64 has reported following issues:

 list.c:140:11: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 file.c:572:51: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 file.c:850:15: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 file.c:865:15: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 delta.c:199:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
 parse.c:80:12: error: this statement may fall through [-Werror=implicit-fallthrough=]
 parse.c:81:12: error: this statement may fall through [-Werror=implicit-fallthrough=]
 file.c:572:51: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 file.c:850:15: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 file.c:865:15: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 delta.c:199:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
 parse.c:80:12: error: this statement may fall through [-Werror=implicit-fallthrough=]
 parse.c:81:12: error: this statement may fall through [-Werror=implicit-fallthrough=]
 ucimap.c:146:16: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:151:17: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:243:34: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:247:9: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:254:39: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:258:9: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:285:34: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:363:17: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:563:12: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:753:18: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
 ucimap.c:879:17: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]

Signed-off-by: Petr Štetiar <ynezz@true.cz>