Add missing IO::SEEK_DATA and IO::SEEK_HOLE constants

[postmodern]

glibc's stdio.h does define SEEK_DATA and SEEK_HOLE and CRuby does support them if they are defined. TruffleRuby should also define these constants, if stdio.h also defines them.

TruffleRuby-22.3.0

IO.constants.grep(/SEEK/)
# => [:SEEK_CUR, :SEEK_SET, :SEEK_END]

CRuby 3.1.2

IO.constants.grep(/SEEK/)
# => [:SEEK_SET, :SEEK_CUR, :SEEK_END, :SEEK_DATA, :SEEK_HOLE]

[eregon]

Thank you for the report.

[andrykonchin]

Fixed in 279c250.