separate kindle and pdf targets

- make `docs` and `html` default
fix Issue 11396 - Function alias declaration not valid according to spec
fix Issue 12802 - Allow optional 'StorageClasses' for new alias syntax
document implicit conversion rules
Merge pull request #583 from WalterBright/imp-conv

document implicit conversion rules
Merge pull request #582 from 9rnsr/fix_aliasdecl

Issue 11396 & 12802 - Allow optional 'StorageClasses' for old/new alias syntax
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