[gpm] [request] link sub-binaries against libgpm.so instead of libgpm.a

[Mike Frysinger]

for the sake of space, can we change the targets in src/Makefile.in to depend 
on libgpm.so and have it link against libgpm.so instead of libgpm.a ?  it 
makes for a small bit of space saving :)

for example, gpm-root does this:
    $(CC) @LDFLAGS@ $(LDFLAGS) -o $@ $@.o @LIBS@ $(LIBS) lib/libgpm.a
-mike