Orage 4.8.0 fails to compile on Solaris, with the following errors

gcc -DHAVE_CONFIG_H -I. -I..    -DPACKAGE_DATA_DIR=\""/packages/xfce48/share"\" -DPACKAGE_LOCALE_DIR=\""/packages/xfce48/share/locale"\" -g -O2 -MT tz_convert-tz_convert.o -MD -MP -MF .deps/tz_convert-tz_convert.Tpo -c -o tz_convert-tz_convert.o `test -f 'tz_convert.c' || echo './'`tz_convert.c
tz_convert.c:22:19: error.h: No such file or directory
tz_convert.c:1435: warning: "struct FTW" declared inside parameter list
tz_convert.c:1435: warning: its scope is only this definition or declaration, which is probably not what you want
tz_convert.c: In function `file_call':
tz_convert.c:1446: error: dereferencing pointer to incomplete type
tz_convert.c:1451: error: `FTW_CONTINUE' undeclared (first use in this function)
tz_convert.c:1451: error: (Each undeclared identifier is reported only once
tz_convert.c:1451: error: for each function it appears in.)
tz_convert.c:1470: error: dereferencing pointer to incomplete type
tz_convert.c:1473: error: `FTW_SKIP_SUBTREE' undeclared (first use in this function)
tz_convert.c:1477: error: dereferencing pointer to incomplete type
tz_convert.c:1480: error: dereferencing pointer to incomplete type
tz_convert.c: In function `main':
tz_convert.c:1617: error: `FTW_ACTIONRETVAL' undeclared (first use in this function)

there's an identical set of errors for tz_zoneinfo_read.c

There are two problems:

1. error.h doesn't exist on Solaris, and is non-standard. I suspect that #including it is an error and unnecessary on all platforms, so I would just delete the #include

2. The FTW_CONTINUE, FTW_SKIP_SUBTREE, and FTW_ACTIONRETVAL are GNU extensions and aren't valid in portable code.