NetBSD changes from scottr: VT220-related emulation additions:  - Add reset attribute sequences for bold, underline, and reverse  - Add insert/delete line sequences  - Recognize but ignore G0/G1 character set sequences
NetBSD changes from scottr:
VT220-related emulation additions:
 - Add reset attribute sequences for bold, underline, and reverse
 - Add insert/delete line sequences
 - Recognize but ignore G0/G1 character set sequences

Performance:
 - Speed up clear_line() when clearing the entire line

Also, some stylistic changes for checking/setting scroll region bounds
and in putc_getpars().

These changes make the ITE work properly with the 1.2 termcap file.

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