update detection of compiler C++11 features

rewrite bsls_compilerfeatures.h with more precise C+11 feature detection

replace use deprecated macro BSLS_PLATFORM_CMP_VER_MAJOR

Note: v1.0 of r-value references were supported in gcc 4.3, but the prior version of bsls_compilerfeatures.h marked support in gcc 4.5 (which supports v2.1 of r-value references).  I have preserved that behavior in this pull request.

Aside: due to substantial number of changes, it will probably be easier to review the bsls_compilerfeatures.h as a standalone file or as a split diff, rather than as a unified diff.