unneeded macros in xdt-depends.m4

Submitted by Christoph Mende

Assigned to Xfce Bug Triage

Link to original bug (#7462)

Description

xdt ships xdt-depends.m4 with XDT_CHECK_LIB{SM,X11,XPM} those three libs ship pkg-config files though (sm, x11 and xpm resp.), which should be preffered, especially since virtually all xfce packages use pkg-config anyway.

Version: git