[committed] libmudflap _start and gp reloc overflow

[James E Wilson <wilson at specifix dot com>]

This is similar in spirit to one of my bug fixes last week.  libmudflap
has configure code to check for the name of the entry point symbol. 
Unfortunately, it declares the variable as type char, which for a target
like mips-elf means the compiler will assume it is in the small data
section, and then we end up with a gp reloc overflow error from the
linker.

The standard trick to avoid this problem is to declare it as an array of
unbounded size.  This is a little tricky, as this is in m4 macro code
and using square brackets are special quoting characters here, so I used
autoconf quadrigraphs.  I got the idea from the libssp configure.ac
file, and verified it was OK by checking the autoconf manual.

This was tested with a mips-elf --enable-libmudflap build.  I get a
configure failure without this patch.  With this patch (and a toplevel
Makefile FLAGS_FOR_TARGET workaround), libmudflap builds fine.

I have checked in the patch.
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com

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