Solaris libXp was shipped as libXp.so.1 so use that for binary compatibility

--- src/Makefile.am Fri Dec 2 20:41:50 2005

+++ src/Makefile.am Mon Aug 11 14:49:19 2008

@@ -31,5 +31,4 @@

# every platform, so until we change the ABI in an incompatible fashion,

# we have to use -version-number

#

-XP_VERSION=-version-number 6:2:0

-libXp_la_LDFLAGS = $(XP_VERSION) -no-undefined

+libXp_la_LDFLAGS = -version-number 1 -no-undefined