Add `--without-keep-formals` option to configure

[jpellegrini]

Hi @egallesio ! This PR partially addresses issue #260 . It adds optional formal parameter information for closures in core STklos and provided libraries -- but not for primitive procedures.

Description

This adds a new option ot the configure script.

If the user passes --without-keep-formals to configure, then the compiler keep-formals parameter will be true when compiling closures in core STklos and all provided libraries.

However, this does not affect primitive procedures, because they are C functions, and having the C compiler include the code to add the formal parameters is, although possible... Tricky, at least.

How it works:

We have three autoconf variables:

    STR_KEEP_FORMALS="no"    # for output at the end of this script
    KEEP_FORMALS=0           # for tmpcomp (and in the future, C files)
    SCM_BOOT_KEEP_FORMALS="" # for the Makefile compiling the boot image

The tmpcomp file needs to be called in the Makefiles with the shell variable

KEEP_FORMALS set:
KEEP_FORMALS=@KEEP_FORMALS@ tmpcomp ...

For the boot image, the variable SCM_BOOT_KEEP_FORMALS is directly used.

And... Well, autotools is reeeeeally not something I ever got to understand well, so perhaps there are better ways to achieve what I did.

Future work (primitive procedures)

Since primitives are defined as C functions, this becomes tricky.

The options I thought:

• Do not store the formal parameters of primitives in their property list, but rather keep them as a string in the structure. Problem: simple, but would be asymmetric (too different from the way it's done for closures).
• Include the C code to actually set the formals in the property list. Problem: maybe a bit too complex?
• Do not keep formals for primitives. Problem: well, we won't have formals for primitives :)

[jpellegrini]

Forgot to mention: the idea is to have formal parameters included by default, but allow the user to not have them for embedded systems or whatever, where size could be an issue.

[jpellegrini]

The --without-keep-formals name means "without the compiler flag keep-formals", but it sounds a bit strange. Maybe we could change that to --without-formal-arguments? I don't know.