Fixes to usage of iconv, from otaylor. Remap characters which are missing

Fixes to usage of iconv, from otaylor. Remap characters which are missing

* src/vte.c: Fixes to usage of iconv, from otaylor.  Remap characters which are
	missing in the current font to others in the current font, if possible,
	from otaylor.  Change default emulation to "xterm", cleaning up
	confusion over what standout really means.  Reorganize some internals.
	Complain when an application sends us a key-press sequence, as if we
	knew what to do with one of those.
* src/vte.c, src/vte.h: Implement vte_terminal_reset().
* src/debug.c, src/debug.h: Added to centralize some debugging settings.
* everywhere: Punt the question of whether or not to print debug spew to
	run-time, suggested by otaylor.
* termcaps/xterm: Added.