(ITS#8238) mdb_cursor_put() returns inconsistent xcursor

[h.b.furuseth@usit.uio.no]

Full_Name: Hallvard B Furuseth
Version: LMDB 0.9.16
OS: Linux x86_64
URL: ftp://ftp.openldap.org/incoming/Hallvard-Furuseth-150906.diff
Submission from: (NULL) (81.191.45.5)
Submitted by: hallvard


Replace printf("oops!\n") with mdb_cassert(mc, 0) in cursor_chk().
Add
	if (!rc && mc->mc_xcursor)
		mdb_cursor_chk(&mc->mc_xcursor->mx_cursor);
just before mdb_cursor_put() returns rc above "bad_sub:".
Diff for this enclosed.

$ make -s clean test CPPFLAGS="-DMDB_DEBUG"
$ ./mtest4
mdb.c:1500: Assertion '0' failed in mdb_cursor_chk()