Squash warnings.

Reviewed by goodell.
Static functions do not need to be name-spaced.

Reviewed by goodell.
Make the InitPG naming consistent.

Avoid camel-cased names.

Reviewed by goodell.
Reorder C and C++ compiler search list.

Use similar compiler search ordering for C and C++ as Fortran.  Some
of the compilers, such as gcc, do not make sense in the C++ compiler
search list, but this patch does not eliminate them.

Reviewed by goodell.
tt#1817: ensure dependencies for PAC_PROG_CC

`PAC_PROG_CC` should always come before `AC_PROG_CC` if the former is
used anywhere in a configure script.  Otherwise one of the many (often
standard) macros which `AC_REQUIRE([AC_PROG_CC])` might inadvertently
bypass the user's desired logic.  The `AC_BEFORE` call here will cause
an autogen-time warning to be emitted if the order is accidentally
interchanged.

Reviewed-by: balaji
fix PAC_PROG_CC ordering in configure.ac scripts

If you get a message like this:

```
configure.ac:30: warning: AC_PROG_CC was called before PAC_PROG_CC
confdb/aclocal_cc.m4:10: PAC_PROG_CC is expanded from...
configure.ac:30: the top level
```

but can't seem to figure out where the earlier AC_PROG_CC macro is
coming from, then you can run autoconf directly with the
`--trace=AC_PROG_CC` argument for more information.

Reviewed-by: balaji
tt#1817: move configure subdir exports earlier

We already were exporting these variables for the "main" subdirs, such
as the configured device/channel/netmod.  The bug was that we weren't
setting these exports in time for OPA or MPL to pick them up.  When
[1a1ff11e] came along and reordered the compiler search list, this
caused MPICH to choose `cc` and OPA to choose `gcc`, which don't agree
on the validity of certain warning flags.  So `--enable-strict=c99`
causes OPA's configure to fail because of a bad compiler flag exported
by the top level.

An alternative "fix" to this commit is to ensure that every single
subdir package uses exactly the same logic in order to select compilers
and compiler options.  This seems much more difficult to ensure.

Reviewed-by: balaji