Fix for #1772 - problem building on SunOS with F77=f90

The problem was a missing declaration in the Fortran test programs
in configure.  While an error for all systems, this was first observed
to fail on SunOS with F77=f90.
un-break `--enable-strict` when using clang

It turns out that `--enable-strict` stopped working at some point when
building with clang.  It would treat the conftest program which was
intended to elicit a warning as being completely erroneous.  My fix is
to instead emit a program with more modest intentional bugs so that we
will get simple warnings which most compilers will detect.

Reviewed-by: balaji
strict: add `-Werror-implicit-function-declaration`

We want to fail-fast when these obvious bugs are spotted by the
compiler, rather than much later when we attempt to link `examples/cpi`.

The biggest risk to this sort of change is that it _might_ break some
subsequent autoconf-layer tests which use implicit functions.

Reviewed-by: balaji
use C99-standard `__VA_ARGS__`

Use C99-standard `__VA_ARGS__` instead of a non-standard GCC extension
that does the same thing.

This version based on code review feedback from Pavan.

No reviewer.
fix uninitialized variable warnings

These were not spotted earlier because our `--enable-strict`
functionality was broken, especially under clang.

Reviewed-by: balaji
Begin cleaning up error reporting
Removed and fixed some FIXMEs
Bug fixes in the PMI keyval allgather code from [3ba0a7f].

1. We had forgotten to distribute the pre-initialized keyvals in the
spawn code to the new proxies.

2. We used a global static for keeping track of the previously
distributed keyvals, instead of a per-KVS-space static.

Fixes tt#1814.

No reviewer.