build manuals included from osmo-gsm-manuals.git

Moved to doc/manuals/, with full commit history, in preceding merge commit.
Now incorporate in local the build system.

Build with:

$ autoreconf -fi
$ ./configure --enable-manuals
$ make

Shared files from osmo-gsm-manuals.git are found automatically if
- the repository is checked out in ../osmo-gsm-manuals; or
- if it osmo-gsm-manuals was installed with "make install"; or
- OSMO_GSM_MANUALS_DIR is set.

Related: OS#3385
Change-Id: I92c0f771d4ffc2b0401d26e25cb0b3817e6f95ea
diff --git a/doc/manuals/osmobsc-usermanual.adoc b/doc/manuals/osmobsc-usermanual.adoc
index 1984678..eec77d7 100644
--- a/doc/manuals/osmobsc-usermanual.adoc
+++ b/doc/manuals/osmobsc-usermanual.adoc
@@ -5,39 +5,39 @@
 Harald Welte <hwelte@sysmocom.de>
 
 
-include::../common/chapters/preface.adoc[]
+include::./common/chapters/preface.adoc[]
 
-include::chapters/overview.adoc[]
+include::{srcdir}/chapters/overview.adoc[]
 
-include::chapters/running.adoc[]
+include::{srcdir}/chapters/running.adoc[]
 
-include::chapters/control.adoc[]
+include::{srcdir}/chapters/control.adoc[]
 
-include::chapters/counters.adoc[]
+include::{srcdir}/chapters/counters.adoc[]
 
-include::chapters/handover.adoc[]
+include::{srcdir}/chapters/handover.adoc[]
 
-include::../common/chapters/vty.adoc[]
+include::./common/chapters/vty.adoc[]
 
-include::../common/chapters/logging.adoc[]
+include::./common/chapters/logging.adoc[]
 
-include::../common/chapters/bts.adoc[]
+include::./common/chapters/bts.adoc[]
 
 include::{srcdir}/chapters/bts-examples.adoc[]
 
-include::../common/chapters/bsc.adoc[]
+include::./common/chapters/bsc.adoc[]
 
-include::../common/chapters/abis.adoc[]
+include::./common/chapters/abis.adoc[]
 
-include::../common/chapters/control_if.adoc[]
+include::./common/chapters/control_if.adoc[]
 
-include::../common/chapters/cell-broadcast.adoc[]
+include::./common/chapters/cell-broadcast.adoc[]
 
-include::../common/chapters/port_numbers.adoc[]
+include::./common/chapters/port_numbers.adoc[]
 
-include::../common/chapters/bibliography.adoc[]
+include::./common/chapters/bibliography.adoc[]
 
-include::../common/chapters/glossary.adoc[]
+include::./common/chapters/glossary.adoc[]
 
-include::../common/chapters/gfdl.adoc[]
+include::./common/chapters/gfdl.adoc[]