patch to optionally relax paren expression handling

[Ian Lance Taylor]

   Date: Fri, 23 Jun 2000 18:04:51 +1000
   From: matthew green <mrg@cygnus.com>

   i need the following patch (plus the relevant #define in tc-foo.h) for
   a new target i am working on.  the instruction i am trying to assemble
   looks like this:

	   insn	(a5), d2

   the problem is that while assembling an instruction, the parser tests
   several wrong instructions before finding the correct instruction.
   unfortunately, some of the wrong instructions expect a value as the
   first operand on this insn, so when parsing the `(a5)' above, it attempts
   to evaluate this as a math grouping, but this fails, and a call to
   as_bad() is taken, causing the assemble to fail.  with the following
   patch, when RELAX_PAREN_GROUPING is defined, a mis-matched '()' will
   not call as_bad().  this fixes my problem and allows the assembler to
   find the correct instruction and generate the right output.  i also
   have reworked the increment of input_line_pointer and corrected the
   as_bad() error message in the '[' case.

For something like this, I think it makes a lot more sense to use a
run time switch rather than a compile time switch.  After all, you
probably do want the error for something like
    .long (1

Pass the appropriate parameter when trying to parse the expression
from your tc-foo.c file, and arrange for a return value indicating an
unparseable expression.

Ian