Fix unused variable warnings in bslstl_string
Fix unused variable warnings in bslstl_string

Import internal commit e8648e2d78bba2d8e5f18dee173ade8110d32ee5

apaprocki/bde,mversche/bde,saxena84/bde,abeels/bde,dbremner/bde,bloomberg/bde,bloomberg/bde-allocator-benchmarks,abeels/bde,osubboo/bde,RMGiroux/bde-allocator-benchmarks,jmptrader/bde,dharesign/bde,gbleaney/Allocator-Benchmarks,mversche/bde,RMGiroux/bde-allocator-benchmarks,mversche/bde,bloomberg/bde,osubboo/bde,saxena84/bde,che2/bde,jmptrader/bde,apaprocki/bde,dbremner/bde,bowlofstew/bde,abeels/bde,dharesign/bde,che2/bde,minhlongdo/bde,osubboo/bde,abeels/bde,abeels/bde,abeels/bde,idispatch/bde,minhlongdo/bde,bowlofstew/bde,bloomberg/bde,dharesign/bde,osubboo/bde,frutiger/bde,bloomberg/bde,idispatch/bde,che2/bde,minhlongdo/bde,che2/bde,apaprocki/bde,bloomberg/bde-allocator-benchmarks,bloomberg/bde-allocator-benchmarks,bloomberg/bde-allocator-benchmarks,idispatch/bde,gbleaney/Allocator-Benchmarks,bloomberg/bde-allocator-benchmarks,RMGiroux/bde-allocator-benchmarks,frutiger/bde,bloomberg/bde,bowlofstew/bde,bowlofstew/bde,jmptrader/bde,frutiger/bde,dbremner/bde,gbleaney/Allocator-Benchmarks,saxena84/bde,gbleaney/Allocator-Benchmarks,jmptrader/bde,frutiger/bde,apaprocki/bde,minhlongdo/bde,idispatch/bde,RMGiroux/bde-allocator-benchmarks,dbremner/bde,apaprocki/bde,mversche/bde,saxena84/bde,dharesign/bde,RMGiroux/bde-allocator-benchmarks