merliseclyde/BAS: BAS Version 1.5.3

This release fixes errors identified on CRAN for fedora with clang (there are still remaining problems with debian/clang and solaris)

Fixed errors identified on cran checks https://cran.r-project.org/web/checks/check_results_BAS.html

• initialize R2_m = 0.0 in lm_mcmcbas.c (lead to NA's with clang on debian and fedora )

• switch to default of pivot = TRUE in bas.lm, adding tol as an argument to control tolerance in cholregpovot for improved stability across platforms with singular or nearly singular designs.

• valgrind messages: Conditional jump or move depends on uninitialised value(s). Initialize vectors allocated via R_alloc in lm_deterministic.c and glm_deterministic.c.