To allow users to install asn1c quickly in install, make this directory
to allow standalone execution of install_asn1c_from_source.

The instructions are now:
sudo ls  # open sudo session, required by install_asn1c_from_source
. oaienv # read of default variables
. cmake_targets/tools/build_helper # read in functions
install_asn1c_from_source # install

CMake now takes the option ASN1C_EXEC to select an asn1c to use for
compilation. For instance, run with
cmake .. -GNinja -DASN1C_EXEC=/opt/asn1c/bin/asn1c
or
./build_oai --cmake-opt -DASN1C_EXEC=/opt/asn1c/bin/asn1c
to select the alternative asn1c. For instance, this is important for the
CI to allow to build multiple versions of OAI in parallel that might use
different commits of OAI.

Further, this patch introduces functionality to check for the support of
asn1c options that we require, and alerts the user if they are missing,
alongside a message of how to resolve the problem.

We don't work much on asn1c. The version we use has several bugs.
There is an active community out there that fixes bugs and improves
asn1c. Let's use their version.

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Fix for following CPPCheck warnings
- invalidPrintfArgType
Rebased with latest develop branch w21.
Reverted modifications unrelated to printf issues.

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

There are a number of timers in RRC. Those are not or only partially
implemented, and certainly don't work in F1. Hence, remove them to
replace with a better implementation later.