01-09-18 zconf.h: include <ast_std.h> for __IMPORT__ and __EXPORT__
00-09-11 gzio: don't set verified=1 in check_header() for concatenation
99-11-19 gzio: add missing _PACKAGE_ast
99-09-11 sfdcgzip,sfdclzw: return 1 if discipline pushed
99-08-11 gzio: fix gzread() z_err to keep Z_STREAM_END after check_header()
99-07-17 sfdclzw: don't free disc on SF_CLOSE
99-06-23 fix gzread/gzwrite to return -1 on error (fixes sfio disc loop)
99-02-14 fix SFGZ_SETPOS to flush/sync for mode=='w' only
99-02-04 add SF_CLOSE to output trailer before the underlying stream is closed!
98-12-01 drop lzwWrite and lzwSeek in sfdclzw 
98-11-01 pushed stream buffer size is SF_BUFSIZE
98-10-01 add SFGZ_GETPOS and SFGZ_SETPOS
98-03-19 sfgzip => sfdcgzip
