Log Message:
lang/schema48: Fix bad pthreads detection for DragonFly

The schema48 configure schema has a pthreads test that can't be overridden.
The problem is that it starts with -mt, and it thinks the test passes when
in reality gcc complains.  This commit does a post-patch inline replacement
on the configure script to override the test, and to add -pthread to both
$CFLAGS and $LDFLAGS.