Turn odd framework::LockHelper::getGlobalLock() into an osl::Mutex

...and extract it to framework::GlobalLock::get().

The old lock was actually effectively two different locks,
LockHelper::getGloblaLock() and
LockHelper::getGlobalLock().getShareableOslMutex(), and both were used in
different places.  These places all use the same single osl::Mutex instance now,
but hopefully that does not lead to problems (which it shouldn't, given the
documentation of LockHelper::getShareableOslMutex: "Sometimes we need a osl-
mutex for sharing with our uno helper ... What can we do? We must use a
different mutex member :-( I HOPE IT WORKS!").

Of course, the "TODO: This presumable should return the SolarMutex" still
applies.

Change-Id: I7caea3241d1b70a00272fe1f2214c071ef22cf2c
Remove unused function declaration

Change-Id: I82ac945e5d1fba82047a7902782893d01eda34e3
Remove newly unused framework::Guard

Change-Id: I49650bfd036c5df22f81c3e8cf30bc0795154a30
Remove newly unused framework::LockHelper class

...and make LockHelper::getGlobalLock() FWI_DLLPUBLIC again (so there's a single
such lock, not one per library).

Change-Id: I0aed77333dc93cdf1c7dd7b96620fb7a8eb3dd64