Detect Ghostscript for 32- or 64-bit installation

[arcadian]

Currently, only the 32-bit version of Ghostscript is detected when trying to access a postscript file such as a PDF. On 64-bit systems with only the 64-bit version of ghostscript installed, the message that this software is needed still appears. Having it check either location would accommodate this scenario.

[xnview]

XnView is 32bits, so only gs 32bits can be used