needs <limits.h>.  Update scripts/reference_exported_symbols.txt and
src/proj_symbol_rename.h.

This is mostly to have better OSSFuzz report. Currently a lot
of bug summaries are like
`proj4/standard_fuzzer: Divide-by-zero in s_inverse`

By prefixing the projection name, we will get better reports, like
`Divide-by-zero in airy_s_inverse`

This also makes it slightly easier to set a breakpoint by
function name.

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=14421
Credit to OSS Fuzz

- 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.