Public alpha 156

• LaTeX support for more commands and features
• big numbers, strings, qids and unparsed tokens are now broken across multiple lines in LaTeX to avoid an "Overfull \hbox"
• fixed bug where bad LaTeX was generated by show mod for certain characters in metadata
• added =># search type
• fixed bug where srewrite could miss a rewrite due to a side-effect from a condition
• equations with both variant and nonexec attributes produce an advisory and are no longer used for variant narrowing
• in/load/sload no longer attempt to read non-regular files
• increased line length and history size with Tecla
• the narrow command now respects frozen positions