syncs pkg install help message with pkg-install.8 man page
Merge remote-tracking branch 'upstream/master'
Remove empty OPTIONS section from pkg-add and pkg-shlib mans
Cleanup trailing whitespace
Merge remote-tracking branch 'z0nt/master'

* z0nt/master:
  Remove empty OPTIONS section from pkg-add and pkg-shlib mans
Emit explanation in DEVELOPER_MODE for the fatal error
Error when neither www or desc is defined in the manifest
Import mongoose into pkgng to be used as a plugin
Add mongoose plugin for serving files into pkgng

* Useful in case you don't have a web server installed and want simply
  to serve a package repository to clients or test something out
* Uses mongoose for making the directory available through HTTP
* Example usage 'pkg serve -d /path/to/pkgng-packages'
Re-work a bit the mongoose plugin
Move plugin files to the plugin/ directory
Add a Makefile for the pkg-plugin-serve plugin for building mongoose and the plugin itself
Add a README for the pkg-plugin-serve mongoose plugin
Include mongoose' includes when building the plugin
Print some information when serving files through mongoose
Check if the provided directory exists before serving it through 'pkg serve'
Do not allow duplicate plugin names
Fix with recent clang

Thanks rdivacky
Now use a hash table for plist keywords
Store files has a hash table