Prevent a virtual table from being destroyed while it is in use.

Also: replace Vdbe.inVtabMethod with sqlite3.nVDestroy.  Simplify the
EXPLAIN output for P4.pVtab to only show the sqlite3_vtab pointer.

FossilOrigin-Name: cbeb9a1aed8ce3fb569a7717ad03c7c058b68de6

diff --cc manifest
index 9bc40202193c5d01eb999349fbcf2480172cd255,e76179efbf7658ff56d1ec727adeb2b2c2585742,f7fe0c82242381ac893f7757fbd35402da81bb99..d1020a6d135c64f62a3c8b012d71560eaa6fb8bb
--- 1/manifest
--- 2/manifest
--- 3/manifest
+++ b/manifest
@@@@ -1,5 -1,5 -1,5 +1,5 @@@@
-  C Disable\sloadable\sextensions\sin\sthe\scommand-line\sshell\son\sVxWorks\suser-space.
-  D 2015-03-23T21:32:50.879
 - C Simplify\sthe\sEXPLAIN\soutput\sof\svirtual\stable\sP4\sparameters\sto\sonly\sshow\sthe\npointer\sto\sthe\ssqlite3_vtab\sobject\sand\somit\sthe\ssqlite3_module\sobject.
 - D 2015-03-24T14:57:02.437
  -C Add\stests\sto\scheck\sthat\sattempting\sto\sDROP\sa\svirtual\stable\swhile\sit\sis\suse\sdoes\snot\scause\sproblems.
  -D 2015-03-24T14:57:21.959
+++C Prevent\sa\svirtual\stable\sfrom\sbeing\sdestroyed\swhile\sit\sis\sin\suse.\nAlso:\sreplace\sVdbe.inVtabMethod\swith\ssqlite3.nVDestroy.\s\sSimplify\sthe\nEXPLAIN\soutput\sfor\sP4.pVtab\sto\sonly\sshow\sthe\ssqlite3_vtab\spointer.
+++D 2015-03-24T16:43:34.928
   F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
   F Makefile.in 88a3e6261286db378fdffa1124cad11b3c05f5bb
   F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@@@ -293,11 -293,11 -293,11 +293,11 @@@@ F src/update.c 3c4ecc282accf12d39edb8d5
   F src/utf.c fc6b889ba0779b7722634cdeaa25f1930d93820c
   F src/util.c 98a7627ca48ad3265b6940915a1d08355eb3fc7e
   F src/vacuum.c 9460b9de7b2d4e34b0d374894aa6c8a0632be8ec
-  F src/vdbe.c bd793ed436edccaf264ec969ac92c9b5f4b41d64
+  F src/vdbe.c bbfede5a8a6908b3ddcd55fdb0b2301288dd4754
   F src/vdbe.h 6fc69d9c5e146302c56e163cb4b31d1ee64a18c3
-  F src/vdbeInt.h bb56fd199d8af1a2c1b9639ee2f70724b4338e3a
+  F src/vdbeInt.h 9cbaa84f53ddd2d09a0cf61a94337a3a035d08a0
   F src/vdbeapi.c 583d56b129dd27f12bed518270de9ebe521e6a75
-  F src/vdbeaux.c 23390670e64f011f3fed8f38a2f25aaccacb74d2
  -F src/vdbeaux.c 056eefd33ef4457240b6d3156a96201579face0a
+ +F src/vdbeaux.c 413dc496248ac18eb0c19e35e86bb1ffd47b8907
   F src/vdbeblob.c 4f2e8e075d238392df98c5e03a64342465b03f90
   F src/vdbemem.c c0dc81285b7571b0a31c40f17846fe2397ec1cd9
   F src/vdbesort.c 919717d7599fa31d343ec28bffd0f9e91a4ff5f6
@@@@ -1246,7 -1246,7 -1246,7 +1246,9 @@@@ F tool/vdbe_profile.tcl 67746953071a9f8
   F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
   F tool/warnings.sh 0abfd78ceb09b7f7c27c688c8e3fe93268a13b32
   F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-  P 6fc4e79a2350295a15ac464593ad39d904953041
-  R f88d42f63f5075e0fafdf77b9c8623bb
 --P 116c99823022c017946b6088878a2d46759deb6e
 - R 5f471e8babb874f26a1b4c65b62f02f6
  -R 791eb1db9d6d4dcf9879622b22bdbc4e
  -U dan
  -Z 5721bb8cdc400d9869a3df977b6ecfb6
+++P 0ee2d38deb35aefc55395e86984a9a773caf6218 85610bbbc60cb4a6ec856123447fdb2ba948e52f 5ee625b1980f9fab6294d308349dfd9ba960b60b
+++R 5e10f0a3ec239c969328e02883201fd9
+++T +closed 5ee625b1980f9fab6294d308349dfd9ba960b60b
+++T +closed 85610bbbc60cb4a6ec856123447fdb2ba948e52f
  +U drh
-  Z b5778fea5ecdfe311fd40aa2979f5026
 - Z ffb5a79aea5fc49ed872d8dd5ea0b00b
+++Z 4c6da71fa5b7897deec943a0cbeb333e

diff --cc manifest.uuid
index 4f62d697cbd8d5fd353b92f4e42900fce0630b44,445a1dff5efc976d3d999eb63c9526cc3edbd86b,5b0b4a1607122be3c36eee9d2026e66559b4cac5..83e3226971c815d9189ff1767cc68b49707eead4
--- 1/manifest.uuid
--- 2/manifest.uuid
--- 3/manifest.uuid
+++ b/manifest.uuid
@@@@ -1,1 -1,1 -1,1 +1,1 @@@@
-  0ee2d38deb35aefc55395e86984a9a773caf6218
 - 85610bbbc60cb4a6ec856123447fdb2ba948e52f
  -5ee625b1980f9fab6294d308349dfd9ba960b60b
+++cbeb9a1aed8ce3fb569a7717ad03c7c058b68de6