MetaSMT builder, solver and command-line options.
Bug fix in MetaSMTBuilder
getConstraintLog() of MetaSMTSolver explicitly states that this feature is not supported; a test case modified to not fail because of this.
command-line option --use-metasmt declared and defined inside #ifdef SUPPORT_METASMT ... #endif macros
tests in ./test/Feature/ExprLogging.c reverted back to not explicitly differentiate on whether metaSMT is used or not
Removed unnecessary/redundant linking of library boost_thread-mt to klee and kleaver.
Merge pull request #41 from hpalikareva/metasmt-multisolver

Support for KLEE-MultiSolver (http://srg.doc.ic.ac.uk/projects/klee-multisolver/)