Build of tests and apps fails with support for shared libs disabled

Build of tests and apps fails with support for shared libs disabled. It should not.

Steps to reproduce with version 1.3.1:
  $ ./autogen.sh --disable-shared
  $ make clean all check

Output:
Making all in app
make[2]: Entering directory `/dev/rohc/rohc-1.3.x/app'
Making all in tunnel
make[3]: Entering directory `/dev/rohc/rohc-1.3.x/app/tunnel'
gcc -DHAVE_CONFIG_H -I. -I../.. -I../../src/common -I../../src/comp -I../../src/decomp -g -Wall -Wstrict-prototypes -g -O2 -Werror -MT tunnel.o -MD -MP -MF .deps/tunnel.Tpo -c -o tunnel.o tunnel.c
mv -f .deps/tunnel.Tpo .deps/tunnel.Po
/bin/sh ../../libtool --tag=CC --mode=link gcc -g -Wall -Wstrict-prototypes -g -O2 -Werror -L../../src/common/.libs -L../../src/comp/.libs -L../../src/decomp/.libs -o rohctunnel tunnel.o -lrohc_common -lrohc_comp -lrohc_decomp -lm -lpcap -lpcap -lpcap -lpcap -lpcap -lpcap -lpcap
libtool: link: gcc -g -Wall -Wstrict-prototypes -g -O2 -Werror -o rohctunnel tunnel.o -L../../src/common/.libs -L../../src/comp/.libs -L../../src/decomp/.libs /rohc/rohc-1.3.x/src/common/.libs/librohc_common.a /dev/rohc/rohc-1.3.x/src/comp/.libs/librohc_comp.a /dev/rohc/rohc-1.3.x/src/decomp/.libs/librohc_decomp.a -lm -lpcap
/dev/rohc/rohc-1.3.x/src/comp/.libs/librohc_comp.a(rohc_comp.o): In function `rohc_c_context':
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:756: undefined reference to `c_sum_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:758: undefined reference to `c_sum_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:762: undefined reference to `c_sum_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:764: undefined reference to `c_sum_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:789: undefined reference to `c_mean_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:793: undefined reference to `c_mean_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/.libs/librohc_comp.a(rohc_comp.o): In function `c_alloc_contexts':
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:1038: undefined reference to `c_create_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:1039: undefined reference to `c_create_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:1040: undefined reference to `c_create_wlsb'
/dev/rohc/rohc-1.3.x/src/comp/rohc_comp.c:1041: undefined reference to `c_create_wlsb'
[...]
collect2: ld returned 1 exit status
make[3]: *** [rohctunnel] Error 1
make[3]: Leaving directory `/dev/rohc/rohc-1.3.x/app/tunnel'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/dev/rohc/rohc-1.3.x/app'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/dev/rohc/rohc-1.3.x'
make: *** [all] Error 2