Fixes consist in:
- no use of comma operator for multi statement purpose
- avoid confusing comma in for loops first and third clauses
- avoid implicit long to int casts by storing to long, or explicit bound checking before cast

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.

lam0 of inf caused a nan in the cast to int.
Picked +/-1000 for lam0 as a guess for what constitutes reduculously large values.

proj_etmerc.c:361:16: runtime error: nan is outside the range of representable values of type 'int'

Found with autofuzz: UndefinedBehaviorSanitizer: float-cast-overflow

* 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

Some macros seemed to be leftover from earlier code, so I removed them.
Others seemed like they should have been used, but weren't.

There should be no functional change, except the following: in floating-
point arithmetic, x / y is not the same as x * (1.0 / y). It can be
argued that using the multiplication is significantly faster, and the
algorithm is approximative anyway. Otherwise, the constants are
obviously not required.

Also fixes one location in PJ_aitoff.c, where an enumeration value
should have been used.

* Removed remaining traces of the builtin selftest system. Moved all functionality to test/gie

* Updated Appveyor and Travis build scripts

* Another appveyor script update