The big size of coordinateoperation.cpp could require significant amount
of RAM to build it with -O2 level, and cause compiler crashes in some
environments.

while mapping ESRI projections, and map the Behrman projection to
cae with lat_ts=30, lon_0=0

This commit is the result of the squashing of rfc4_dev branch in a single
commit. It implements mostly RFC 4 related work.

* Grid handling:
  - remove obsolete and presumably unfinished implementation of grid catalog functionality
  - all grid functionality is in grids.cpp/.hpp
  - vertical and horizontal grid shift: rework to no longer load whole grid into memory
  - remove hgrids and vgrids member from PJ structure, and store them in hgridshift/vgridshift/deformation structures
  - build systems: add optional libtiff dependency. Must be explicitly disabled if not desired
  - add support for horizontal and vertical grids in GeoTIFF, if libtiff is available
  - add GenericShiftGridSet and GenericShiftGrid classes, relying on TIFF grids, that can be used for generic purpose grid-based adjustment
  - add a +proj=xyzgridshift method to perform geocentric translation by grid. Used for French NTF to RGF93 transformation using gr3df97a.tif grid
  - deformation: add support for +grids= for GeoTIFF grids
  - horizontal grid shift: fix failures on points slightly outside a subgrid (fixes #209)

* File management:
  - add a filemanager.cpp/.hpp to deal with file related work
  - test for legacy proj_api.h fileapi
  - proj.h: add proj_context_set_fileapi() and proj_context_set_sqlite3_vfs_name() (fixes #866)
  - add capability to read resource files from the user writable directory

* Network access:
  - build systems: add optional curl dependency
  - add a curl-based default implementation for network related functionality
  - proj.h: add C API to control network functionality, and optionaly provide network callbacks
  - add data/proj.ini with default settings
  - add a SQLite3 local cache of downloaded chunks
  - add proj_is_download_needed() and proj_download_file()

* Use Win32 Unicode APIs and expect all strings to be UTF-8 (fixes #1765)
  For backward compatibility, if PROJ_LIB content is found to be not UTF-8 or
  pointing to a non existing directory, then an attempt at interpretating it
  in the ANSI page encoding is done.
  proj_context_set_search_paths() now assumes strings to be in UTF-8, and
  functions returning paths will also return values in UTF-8.

Seen when testing transformations between "CR 05" (EPSG:5365) and "CR-SIRGAS" (EPSG:8907)
which require going through their corresponding 3D GeogCRS to find a Helmert
transformation.

- coordinateoperation_internal.hpp: missing 'explicit' keyword
- proj.cpp: unused 'generic' member in enumeration
- init.cpp: useless assignment to a_orig and es_orig, because done again a
            few lines below.
- crs.cpp: unused variable
- datum.cpp: inefficient use of find() function
- io.cpp:
  * missing 'static' qualifier for method
  * useles ternary test (left and right have same value)
- aeqd.cpp: useless assignment of inv and fwd, snice done again a few lines
            below
- isea.cpp: useless assignment of resolution and aperture since done again a
            few lines below, and with default values when params are absent
- mod_ster.cpp: useless assignment of lp.lam, overriden in below code paths.
- stere.cpp: false positive, but better not modify another variable than the
             iterator in a for() loop.

And publish link to corresponding promoted and public OGC doc:
http://docs.opengeospatial.org/as/18-005r4/18-005r4.html