Henceforward, aclocal.m4 will be generated by the 'autoreconf' command.
The 'autoreconf -f -i' command may now emit a warning "Unsupported
attribute section, the test may fail" on some systems, but it will still
generate the proper aclocal.m4 and ./configure files. To suppress this
warning, simply invoke autoreconf with '-I m4' argument:
autoreconf -f -i -I m4
The INSTALL.md has been updated accordingly, and a new 'Notes for
Developers' technical document added, explaining the use of aclocal and
autoreconf, and documenting that these warning messages are of no
concern.
These macros copied in from the Autoconf Macro Archive were missing
support for the following attributes:
- AX_GCC_VAR_ATTRIBUTE() for __attribute__(section("..."))
- AX_GCC_FUNC_ATTRIBUTE() for __attribute__(returns_nonnull)
This commit fixes them. (The versions in aclocal.m4 were already fixed,
but aclocal.m4 is about to be removed from version control.)
