libimcv: Support symlinks introduced by usrmerge

Debian, Ubuntu, Fedora et. al. started to apply usrmerge to their
latest Linux distributions, i.e.  /bin, /sbin, and /lib are now
symbolical links to /usr/bin, /usr/sbin, and /usr/lib, respectively.
Since executables and libraries are contained only once in Linux
packages (e.g. /bin/cp in coreutils but not /usr/bin/cp) this leads
to missing file measurments due to the symlinks when doing remote
attestation.

The new ita_attr_symlinks PA-TNC attribute fixes this problem by
collecting symbolic links pointing to directories on the client
platform.

src/libimcv/Makefile.am

@@ -63,6 +63,7 @@ libimcv_la_SOURCES = \
 	ita/ita_attr_get_settings.h ita/ita_attr_get_settings.c \
 	ita/ita_attr_settings.h ita/ita_attr_settings.c \
 	ita/ita_attr_angel.h ita/ita_attr_angel.c \
+	ita/ita_attr_symlinks.h ita/ita_attr_symlinks.c \
 	os_info/os_info.h os_info/os_info.c \
 	pa_tnc/pa_tnc_attr.h \
 	pa_tnc/pa_tnc_msg.h pa_tnc/pa_tnc_msg.c \
@@ -81,6 +82,7 @@ libimcv_la_SOURCES = \
 	pts/pts_ima_bios_list.h pts/pts_ima_bios_list.c \
 	pts/pts_ima_event_list.h pts/pts_ima_event_list.c \
 	pts/pts_meas_algo.h pts/pts_meas_algo.c \
+	pts/pts_symlinks.h pts/pts_symlinks.c \
 	pts/components/pts_component.h \
 	pts/components/pts_component_manager.h pts/components/pts_component_manager.c \
 	pts/components/pts_comp_evidence.h pts/components/pts_comp_evidence.c \