Because of how Guile saves and restores continuations (by copying the
stack), and how it uses alloca to create space for debug information
on the stack, we must have an alloca() that really does use the stack,
and not one that uses the heap.
To do this, we use the Gnulib "alloca-opt" module instead of "alloca".
This commit also updates the Gnulib sources from the current Gnulib
Git repository.
* configure.in: Use `AC_CONFIG_MACRO_DIR([m4])'. Reverts patch
b01284227e and makes `libtoolize' from
Libtool 2 happier (removes a couple of warnings).
* Makefile.am (ACLOCAL_AMFLAGS): Remove `-I guile-config' since that
directory only contains macros that we distribute, not macros that we
use.
* m4/labels-as-values.m4: New file, checks for computed goto.
* configure.in: Use AC_C_LABELS_AS_VALUES.
* module/system/repl/command.scm (procedure-documentation): Extend the
core's procedure-documentation in an ad-hoc way, so that ,help works.
* module/system/vm/core.scm (program-properties): New function.
(program-documentation): New function.
* src/vm_engine.h (DROP, DROPN): Decrement sp before checking for
underflow.
* src/vm_system.c (call, tail-call): Add some optimized dispatch for some
C functions, so that we can avoid consing and the interpreter if
possible. However currently it seems that I'm always getting the
scm_call_* trampolines back.
