prefix sub-directories containing libraries with 'lib'

... and make sure tests work again after restructuring
diff --git a/openbsc/src/gb/Makefile.am b/openbsc/src/libgb/Makefile.am
similarity index 100%
rename from openbsc/src/gb/Makefile.am
rename to openbsc/src/libgb/Makefile.am
diff --git a/openbsc/src/gb/gprs_bssgp.c b/openbsc/src/libgb/gprs_bssgp.c
similarity index 100%
rename from openbsc/src/gb/gprs_bssgp.c
rename to openbsc/src/libgb/gprs_bssgp.c
diff --git a/openbsc/src/gb/gprs_bssgp_util.c b/openbsc/src/libgb/gprs_bssgp_util.c
similarity index 100%
rename from openbsc/src/gb/gprs_bssgp_util.c
rename to openbsc/src/libgb/gprs_bssgp_util.c
diff --git a/openbsc/src/gb/gprs_bssgp_vty.c b/openbsc/src/libgb/gprs_bssgp_vty.c
similarity index 100%
rename from openbsc/src/gb/gprs_bssgp_vty.c
rename to openbsc/src/libgb/gprs_bssgp_vty.c
diff --git a/openbsc/src/gb/gprs_ns.c b/openbsc/src/libgb/gprs_ns.c
similarity index 100%
rename from openbsc/src/gb/gprs_ns.c
rename to openbsc/src/libgb/gprs_ns.c
diff --git a/openbsc/src/gb/gprs_ns_frgre.c b/openbsc/src/libgb/gprs_ns_frgre.c
similarity index 100%
rename from openbsc/src/gb/gprs_ns_frgre.c
rename to openbsc/src/libgb/gprs_ns_frgre.c
diff --git a/openbsc/src/gb/gprs_ns_vty.c b/openbsc/src/libgb/gprs_ns_vty.c
similarity index 100%
rename from openbsc/src/gb/gprs_ns_vty.c
rename to openbsc/src/libgb/gprs_ns_vty.c