configure fails to detect dlopen on NetBSD

[Former user]

When packaging liblangtag (0.5.3) for NetBSD, we noticed that the ldml modules don't get built. The reason for this is that since under NetBSD, libdl doesn't need to be linked for dlopen(3) - indeed, libdl doesn't exist. I've attached a patch that fixes this detection issue under NetBSD.

[Akira TAGOH]

Fix the module build on NetBSD (fixed issue#7)

Patch from Jaap Boender

→ <<cset 9cedd1cf0f4d>>

[Akira TAGOH]

Fix the module build on NetBSD (fixed issue#7)

Patch from Jaap Boender

→ <<cset e10fd8d66609>>