Include samplerate libs during compilation of libsigproc

On Ubuntu, compilation fails with this error:

libtool: link: g++ -Wall -std=c++0x -fno-rtti -pthread -I/usr/include/gtk-3.0 -I/usr/include/atk-1.0 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/include/harfbuzz -I/usr/include/freetype2 -I/usr/include/pixman-1 -I/usr/include/libpng12 -pthread -I/usr/include/gtk-3.0 -I/usr/include/atk-1.0 -I/usr/include/at-spi2-atk/2.0 -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/cairo -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/glib-2.0 -I/usr/lib/i386-linux-gnu/glib-2.0/include -I/usr/include/harfbuzz -I/usr/include/freetype2 -I/usr/include/pixman-1 -I/usr/include/libpng12 -I/usr/include/unique-3.0 -fopenmp -I../../src -DBUILT_BY=\"buildd@komainu\" -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wl,-Bsymbolic-functions -Wl,-z -Wl,relro -o .libs/aghermann print_version.o main.o globals.o -pthread -Wl,--export-dynamic -fopenmp  ui/sm/liba.a ui/mw/liba.a ui/sf/liba.a ui/mf/liba.a ui/liba.a model/liba.a rk1968/liba.a patterns/liba.a ../libmetrics/.libs/libmetrics.so ../libsigproc/.libs/libsigproc.so ../common/liba.a expdesign/liba.a ../libsigfile/.libs/libsigfile.so -lfftw3 -litpp -lsamplerate -lgsl -lgslcblas -lm -lgthread-2.0 -lgmodule-2.0 -lunique-3.0 -lvte2_90 -lgtk-3 -lgdk-3 -latk-1.0 -lpangocairo-1.0 -lgdk_pixbuf-2.0 /usr/lib/i386-linux-gnu/libcairo-gobject.so -lpango-1.0 -lgio-2.0 -lgobject-2.0 -lglib-2.0 /usr/lib/i386-linux-gnu/libcairo.so -lX11 -lXext -lconfig++ -lfftw3_omp -lpthread -fopenmp -pthread -Wl,-rpath -Wl,/usr/lib/i386-linux-gnu/aghermann
../libsigproc/.libs/libsigproc.so: undefined reference to `src_simple'
collect2: error: ld returned 1 exit status

All needed libraries have to explicitly added to the linker command line. The proposed change does that.