TECO-64 version 200.19.1

Added handler for SIGABRT to reset terminal after assertion failures.
Added undocumented --mung option to facilitate shell script execution of TECO.
Changed loop commands to use static rather than dynamic memory.
Added E_MAX error for exceeding nesting levels for loops and conditionals (32 each).
Improved the handling of O commands inside loops and conditionals.
Revised pi.tec macro to range check macro argument.
Enhanced --argument option to allow both 'm' and 'n' arguments.
Re-wrote pi.tec macro to fix errors and conform to spigot algorithm.
Allowed CTRL/A through CTRL/Z to be used for text delimiters.
Suppress display mode if --exit or -X command-line options used.
Changed scan function for 'I' command to ignore text argument if numeric argument provided.
Created new E_TXT error message for text delimiter violations.
Fixed handling of virtual column when using arrow keys.
Fixed various minor bugs and lint warnings.
Updated documentation as needed.