configure/Makefiles: add checks for Xmu, Xext, and Xdmcp

We also remove sun pro specific options, and do some general cleanup
as well as remove hardcoded library refs like -lXm, -lXext, etc...

cde/programs/dtmail/libDtMail/Common/Makefile.am

@@ -6,7 +6,7 @@ libCommon_a_CXXFLAGS = -I../../include -I../../include/utils -I$(srcdir)/lib \
 		       -DDL_NOT_DYNAMIC -DUSE_SOCKSTREAM
 
 if SOLARIS
-libCommon_a_CXXFLAGS += -DMMAP_NORESERVE -DSPRO_V2
+libCommon_a_CXXFLAGS += -DMMAP_NORESERVE
 endif
 
 libCommon_a_SOURCES = APOPServer.C \

cde/programs/dtmail/libDtMail/RFC/Makefile.am

@@ -6,7 +6,7 @@ libRFC_a_CXXFLAGS = -I../Common -I../../include -I../../include/utils \
 		    -DTTLOCK_OFF
 
 if SOLARIS
-libRFC_a_CXXFLAGS += -DMMAP_NORESERVE -DSPRO_V2
+libRFC_a_CXXFLAGS += -DMMAP_NORESERVE
 endif
 
 libRFC_a_SOURCES = AliasExpand.C           MIMEBodyPart.C \