Improve error handling while incremental searching

- Add lots of error to ignore
- Also avoid error for on_char_pre function
Merge branch 'fix-avoid-searching-error' into dev
spec: fix history spec

- Segmentation fault with histdel()...
Improve incremental cursor position and visual highlight

While searching, now ...

- cursor position is now respect :h {offset} !
- selected visual highlight is updated incrementally
Handle cursor movement for <expr> mapping
Use s:cli.is_expr instead of called_by_non_expr argument

- Add comment
- Remove unneeded silent!
Merge branch 'improve-search-pos' into dev
Fix emulation of visual selected highlight over screen height
Use more appropriate function name

s/pseud_visual_highlight/emulate_visual_highlight
Cache visual highlight once captureing
Use default argument of s:emulate_visual_highlight()
Add NOTE for s:emulate_visual_highlight()
Error handling for s:get_visual_pattern()
Merge branch 'fix-visual-selection' into dev
Separate util and highlight method into autoload file
Merge branch 'separate-file' into dev
Use <SNR><SID>_{funcname} to get funcref
Merge branch 'fix-travis' into dev
Fix sort_pos: it should return -1,0,1 instead of boolean
spec: specify scriptencoding