GUACAMOLE-1026: Correct and clean up FreeRDP presence/absence reporting by configure.

[mike-jumper]

Previously, the name of the library would change depending on which version is installed:

$ ./configure
...
------------------------------------------------
guacamole-server version 1.5.5
------------------------------------------------

   Library status:

     freerdp3 ............ yes
     pango ............... yes
     libavcodec .......... yes
...

and there was no output for the "disabled" case:

...
------------------------------------------------
guacamole-server version 1.5.5
------------------------------------------------

   Library status:

     freerdp ............ 
     pango ............... yes
     libavcodec .......... yes
...

Here, the library name remains constant while version notes are included to the side:

$ ./configure
...
------------------------------------------------
guacamole-server version 1.5.5
------------------------------------------------

   Library status:

     freerdp ............. yes (3.x)
     pango ............... yes
     libavcodec .......... yes
...

and the output of "disabled" is restored:

$ ./configure --without-rdp
...
------------------------------------------------
guacamole-server version 1.5.5
------------------------------------------------

   Library status:

     freerdp ............. disabled 
     pango ............... yes
     libavcodec .......... yes
...