separate kindle and pdf targets

- make `docs` and `html` default
Document -boundscheck=[on|safeonly|off]
Begin 2.066 changelog

Start off with -boundscheck= description.
fix Issue 12740 - DMD accepts invalid version syntax
Merge pull request #585 from 9rnsr/fix12740

Issue 12740 - DMD accepts invalid version syntax
fix implicit conversion table for references
Merge pull request #537 from eco/boundscheck

Document -boundscheck=[on|safeonly|off]
Merge pull request #586 from 9rnsr/fix_conversion_table

fix implicit conversion table for references
Merge pull request #518 from MartinNowak/kindleTarget

separate kindle and latex targets
Update GDC home page
Add GDC links to stable sources, make clearer description of downloads page
Merge pull request #588 from ibuclaw/gdcpage

Update GDC links on downloads
Clarify which CPUs are supported by DMD on which platform
Use lower_underscore names for the DDOX documentation instead of purelowercase.
Merge pull request #593 from schuetzm/dmd-zip-architectures

Clarify which CPUs are supported by DMD on which platform
fix Issue 12813 - Parser is confused between float and UFC syntax
Update index.dd

Announce the start of the 2.066 beta and provide convenient link to available DConf 2014 videos.
Merge pull request #594 from s-ludwig/master

Use lower_underscore names for the DDOX documentation instead of purelowercase.
URL encode characters in the "DConf 2014 videos" link so the link actually works
Merge pull request #596 from JinShil/patch-1

URL encode characters in the "DConf 2014 videos" link