maint: refer to correct license file

maint: refer to correct license file

Now that COPYING no longer contains the text of the LGPL,
modify the LGPLv2-only files from vbox to call out the
correct file.

* src/vbox/vbox_CAPI_v2_2.h: Refer to correct file.
* src/vbox/vbox_CAPI_v3_0.h: Likewise.
* src/vbox/vbox_CAPI_v3_1.h: Likewise.
* src/vbox/vbox_CAPI_v3_2.h: Likewise.
* src/vbox/vbox_CAPI_v4_0.h: Likewise.
* src/vbox/vbox_CAPI_v4_1.h: Likewise.
* src/vbox/vbox_V2_2.c: Likewise.
* src/vbox/vbox_V3_0.c: Likewise.
* src/vbox/vbox_V3_1.c: Likewise.
* src/vbox/vbox_XPCOMCGlue.c: Likewise.
* src/vbox/vbox_XPCOMCGlue.h: Likewise.
* src/vbox/vbox_driver.c: Likewise.
* src/vbox/vbox_driver.h: Likewise.
* src/vbox/vbox_tmpl.c: Likewise.
* src/vbox/vbox_V3_2.c: Copy license notice from vbox_V3_1.c.
* src/vbox/vbox_V4_0.c: Likewise.
* src/vbox/vbox_V4_1.c: Likewise.
* src/vbox/README: Mention copyright issues; this particular
file contains no code and therefore does not need LGPL.

Signed-off-by: Eric Blake <eblake@redhat.com>