* libtool.m4 (no_undefine_flag) [solaris*]:  Don't set this flag
if GCC < 3.0 with native ld, which introduces a dependency on
libgcc.a under certain circumstances, which in turn violates
-no-undefined.  Also display a prominent configure time warning if
the buggy combination of GCC and ld is detected.
(AC_LIBTOOL_HEADER_ASSERT):  libltdl falls foul of this bug
because assert requires __eprintf from libgcc.a.  This macro
detects the combination of GCC and ld that produce this problem,
and pretends that assert.h does not exist...
* libltdl/ltdl.c (HAVE_ASSERT_H):  ...so that assertions can be
disabled in libltdl.  Otherwise the library would only be useable
when linking using gcc, or by manually adding libgcc.a to the link
line of the application that uses libltdl.
* ltdl.m4 (AC_LIB_LTDL):  Require AC_LIBTOOL_HEADER_ASSERT.
* doc/PLATFORMS:  Updated.