bool improvements

Change-Id: I757e19313576d2c3d13af1cb720f182f0de91613
Let C++ inline functions return bool instead of sal_Bool

...to improve diagnosing misuses of boolean expressions in client code (cf.
compilerplugins/clang/implicitboolconversion.cxx).  This change should be
transparent to client code.

Change-Id: Ibf43c5ded609b489952e1cc666cac1e72ffa2386