Module for designing keyboard layouts

Changes for 0.78

• Document the valid way to distinguish character-input events from bind-to-actions events on Windows. (Untested. Warnings are put to compare “the old way” and “the new way”.) A lot of cleanup and cross-linking in the docs. The first pass of cleaning up the TODO section. The “wrong-keynames” head2 slipped down: became under a wrong head1. Correction/inversion of the recommendation to consume the bitmap of lCtrl into rAlt. Would not put NOALTGR into ATTRIBUTES. Strip common-with-lCtrl bits from rAlt in MODIFIERS. Correct 1 POD syntax error. Need to emphasize in the documentation that key releases of HEX-digit keys are important for input-by-numbers! Clarify ALTNUMPAD_BIT and OEM codepage.
• examples/HOWTO-install-deinstall-and-tables.txt New file (from ilyaz.org)
• examples/klc-layout2human.pl Change funny spaces not to ␣, but to ⍽.
• izKeys-visual-maps-base.html Add a stub for Vietnamese input.
• examples/klc2c.pl Add comment to the MODIFIER section about the effect of KLLF_ALTGR.
• examples/dumper-msg.c New file. Do-only-trivial-reports initial implementation of untangling keyboard input.