Accept output arguments to benchmark functions

This patch adds the ability to accept output arguments to functions
being benchmarked, by nesting the argument type in <> in the args
directive.  It includes the sincos implementation as an example, where
the function would have the following args directive:

  ## args: double:<double *>:<double *>

This simply adds a definition for a static variable whose pointer gets
passed into the function, so it's not yet possible to pass something
more complicated like a pre-allocated string or array.  That would be
a good feature to add if a function needs it.

The values in the input file will map only to the input arguments.  So
if I had a directive like this for a function foo:

  ## args: int:<int *>:int:<int *>

and I have a value list like this:

1, 2
3, 4
5, 6

then the function calls generated would be:

foo (1, &out1, 2, &out2);
foo (3, &out1, 4, &out2);
foo (5, &out1, 6, &out2);

1 files changed, 27 insertions, 0 deletions

diff --git a/benchtests/sincos-inputs b/benchtests/sincos-inputs
new file mode 100644
index 0000000000..3df4d2a23b
--- /dev/null
+++ b/benchtests/sincos-inputs
@@ -0,0 +1,27 @@
+## includes: math.h
+## args: double:<double *>:<double *>
+0.9
+2.3
+3.7
+3.9
+4.0
+4.7
+5.9
+0x1.000000cf4a2a1p0
+0x1.0000010b239a8p0
+0x1.00000162a932ap0
+0x1.000002d452a11p0
+0x1.000005bc7d86cp0
+## name: 768bits
+0.93340582292648832662962377071381
+2.3328432680770916363144351635128
+3.7439477503636453548097051680088
+3.9225160069792437411706487182528
+4.0711651639931289992091478779912
+4.7858438478542097982426639646292
+5.9840767662578002727968851104379
+0x1.000000cf4a2a2p0
+0x1.0000010b239a9p0
+0x1.00000162a932bp0
+0x1.000002d452a10p0
+0x1.000005bc7d86dp0