Implement RFC 2: Initial integration of "GDAL SRS barn" work

This work mostly consists of:
- a C++ implementation of the ISO-19111:2018 / OGC Topic 2
  "Referencing by coordinates" classes to represent Datums,
  Coordinate systems, CRSs (Coordinate Reference Systems) and
  Coordinate Operations.
- methods to convert between this C++ modeling and WKT1, WKT2
  and PROJ string representations of those objects
- management and query of a SQLite3 database of CRS and Coordinate Operation definition
- a C API binding part of those capabilities

This is all-in-one squashed commit of the work of
https://github.com/OSGeo/proj.4/pull/1040

1 files changed, 5 insertions, 0 deletions

diff --git a/docs/source/conf.py b/docs/source/conf.py
index 434e4d73..612c7c7e 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -34,6 +34,7 @@ import bibstyle
 extensions = [
     'sphinx.ext.mathjax',
     'sphinxcontrib.bibtex',
+    'breathe',
 ]
 
 # Add any paths that contain templates here, relative to this directory.
@@ -346,3 +347,7 @@ texinfo_documents = [
 
 # If true, do not generate a @detailmenu in the "Top" node's menu.
 #texinfo_no_detailmenu = False
+
+breathe_projects = {
+    "cpp_stuff":"../build/xml/",
+}