[gfortran] Fix PRs 14771, 20894, 25048 : keep track of parentheses

[Tobias dot Schlueter at Physik dot Uni-Muenchen dot DE]

This is the patch I had originally sent to the g95 lists in October 2002,
updated to our current tree.  It makes us keep track of parentheses around
numerical expressions, and makes us reject a number of instances of wrong code
(PR 20894, 25048), and the bug Walt Brainerd reported as fc107, where we got
pass-by-value wrong.

The patch itself is fairly straightforward: a new intrinsic operator
(INTRINSIC_PARENTHESES) is added, a numerical expression is wrapped as operand
to this operator, if it is found inside parentheses.  Then straightforward code
for simplification and resolution is added, following the lines of the unary
plus operator.  Finally expression translation is taught about the parentheses,
and everything falls into its place, and the bugs are fixed.

Built and tested on i686-pc-linux GNU, I'm seeing a regression with
unf_io_convert_4.f90 with and without the patch, but other than that the
testsuite run is clean.  ChangeLog below, patch and new testcases attached.  Ok
for the trunk and 4.1?

Regards,
- Tobi

	PR fortran/14771
	* gfortran.h (gfc_intrinsic_op): Add INTRINSIC_PARENTHESES.
	* dump-parse-tree (gfc_show_expr): Handle INTRINSIC_PARENTHESES.
	* expr.c (simplify_intrinsic_op): Treat INTRINSIC_PARENTHESES as
	if it were INTRINSIC_UPLUS.
	* resolve.c (resolve_operator): Handle INTRINSIC_PARENTHESES.
	* match.c (intrinsic_operators): Add INTRINSIC_PARENTHESES.
	* matchexp.c (match_primary): Record parentheses surrounding
	numeric expressions.
	* module.c (intrinsics): Add INTRINSIC_PARENTHESES for module
	dumping.
	* trans-expr.c (gfc_conv_expr_op): Handle INTRINSIC_PARENTHESES.

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