dropping STAR_ENABLE_FILE_LOCKING environmental variable

digging around I came across getenv("STAR_ENABLE_FILE_LOCKING") in
tools. I was aware of SAL_ENABLE_FILE_LOCKING, but unaware of
STAR_ENABLE_FILE_LOCKING

We don't seem to have documented STAR_ENABLE_FILE_LOCKING anywhere, and
random web searches don't seem to show that its generally known, 

Any uses of it, e.g. now defunct
http://cgit.freedesktop.org/libreoffice/build/tree/patches/dev300/ubuntu-soffice-config.diff?h=ooo-build-3-2
are of the form of
export STAR_ENABLE_FILE_LOCKING=0
which looks like it attempts to *disable* it, even though actually
setting the variable, regardless of what value its set to, would
*enable* it.

I reckon we should drop the stuff that's hooked off
getenv("STAR_ENABLE_FILE_LOCKING"), any protest against that ?

C.