sl/symproc: add basic handler of CL_BINOP_TRUNC_DIV
sl/cl_symexec: remember to initialize gl variables

... if compiled with SE_DISABLE_SYMCUT, which breaks importGlVar()
sl/symcall: unimplement bogus over-optimization
sl/symcall: plug ctx leak in SymCallCtx::invalidate()
sl/symcall: penalize cache entry updates

Speed!