Fix bounds error in forward-i-search
Bind remaining control characters in the search keymap

New functionality:
  ^L clears the display
  ^N and ^P iterate through the next or previous result
  ^G and ESC-ESC cancel search mode
  ^W erases the previous word to whitespace
Merge pull request #6682 from mbauman/search-bounds

Fix #6671: Check search bounds and bind missing control characters in i-search modes