Closes #1107

We are relying more and more on C99 math functions. On C89 systems where
those functions are not available our own custom versions of those
functions are used instead. So far these has been spread across the code
base. This commit gathers them in the same file and introduces the
proj_math.h header. The build system checks for C99 math functions. If
not found the proj_math.h header make sure that C99 functions are
defined as their pj_ equivalent.

Ideally proj_math.h is included instead of math.h. This removes the need
for any checks against HAVE_C99_MATH in the code making it easier to
read.

For this commit the functions hypot, log1p and asinh has been taken care
of.

* Avoid using angle brackets for PROJ headers.

Switching from #include <proj.h> to #include "proj.h",
and correspondingly for projects.h and proj_api.h,
reduces the risk of accidentally picking up a system
installed older version of the header while building
a new version of PROJ.

* Also handle geodesic.h

* Free format now in cmd lines, in gie, and in init files

* Corrected handling of defaults

* Add demo of integrated definition and validation

* Repair stack-smashing memmove in get_init

* repair paralist corruption, clean up debug output

* Install test files for nmake builds

* Add many improvements following suggestions by @schwehr

* Be consistent in requiring lower case everywhere in gie.c

Also, this Fixes #703 and Fixes #697 

Increase the focus on PJ_COORD as primary datatype: Eliminate use of PJ_TRIPLET etc.

Trim proj.h by removing material that has become unnecessary.

Improve constness

Make proj_factors work in proj.h space, by providing a trimmed down PJ_FACTORS (which even has more meaningful field names)

* Support numerical factors only
* Make sure h positive. Improve some comments
* Let pole overshoot check have effect even for geocentric latitudes
* Factor-typological constants, now all returning false, for backwards compatibility