Moved some functions

Some functions were specific to OS X, but were defined in the `base` plugin. I have moved them to the `osx` plugin:

* pman
* pcurl
* pri

As for `pcurl`, the `osx` plugin already had an existing `prevcurl` function, which was doing the same thing. I've aliased `pcurl` to simply call `prevcurl` to avoid breaking existing installations.

As far as I know the `open -fa $PREVIEW` thing only works on OS X, which means that these functions have only worked on OS X anyway.

plugins/available/base.plugin.bash

@@ -99,33 +99,6 @@ function lsgrep ()
     ls | grep "$*"
 }
 
-function pman ()
-{
-    about 'view man documentation in Preview'
-    param '1: man page to view'
-    example '$ pman bash'
-    group 'base'
-    man -t "${1}" | open -f -a $PREVIEW
-}
-
-function pcurl ()
-{
-    about 'download file and Preview it'
-    param '1: download URL'
-    example '$ pcurl http://www.irs.gov/pub/irs-pdf/fw4.pdf'
-    group 'base'
-    curl "${1}" | open -f -a $PREVIEW
-}
-
-function pri ()
-{
-    about 'display information about Ruby classes, modules, or methods, in Preview'
-    param '1: Ruby method, module, or class'
-    example '$ pri Array'
-    group 'base'
-    ri -T "${1}" | open -f -a $PREVIEW
-}
-
 function quiet ()
 {
     about 'what *does* this do?'