Changes from OPTIM

All conjugate-gradient procedures have been replaced by the limited memory BFGS algorithm of Jorge Nocedal[10], which is much faster. The following OPTIM keywords have been retired: TOLBRENT, DBRENT, MYLINMIN, NOPRINTPARAMS, POWER. There are new keywords: UPDATES, PRINTLEVEL, GTOL and DGUESS (see §4). The following keywords are almost direct replacements: BFGSMIN for CGMIN, BFGSTS for CGTS, BFGSSTEP for CGSTEP, BFGSCONV for CGCONV. However, the arguments required for BFGSCONV and BFGSTS are different. For BFGSCONV only one argument is required, which corresponds to the convergence criterion for the root-mean-square (RMS) force. Further updates are collected in §16.