import oap message parsing / encoding from openbsc.git; AGPL->GPL

In the process, also:
* Change the license from AGPLv3 to GPLv2-or-later;
* correct spelling of 'sysmocom' to lowercase;
* add '2016' to the copyright;
* rename to osmo_*;
* add API docs;
* add logging category DLOAP: define id and add to internal_cat;
* redirect all oap.c logging to DLOAP.

A unit test will follow in a subsequent patch, since it needs a minor tweak for
decoding of boolean values.

The related openbsc change-id is I2f06aaa6eb54eafa860cfed8e72e41d82ff1c4cf.

Tweaked-by: Neels Hofmeyr
Change-Id: If5099e60681a215e798b6675f21813f26769c253
diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am
index 3877f78..4ea55e1 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -22,7 +22,7 @@
 			auth_milenage.c milenage/aes-encblock.c gea.c \
 			milenage/aes-internal.c milenage/aes-internal-enc.c \
 			milenage/milenage.c gan.c ipa.c gsm0341.c apn.c \
-			gsup.c gprs_gea.c gsm0503_conv.c
+			gsup.c gprs_gea.c gsm0503_conv.c oap.c
 libgsmint_la_LDFLAGS = -no-undefined
 libgsmint_la_LIBADD = $(top_builddir)/src/libosmocore.la