glsl: Split code to generate an ir_call out from match_function_by_name.

glsl: Split code to generate an ir_call out from match_function_by_name.

match_function_by_name performs two fairly separate tasks:
1. Hunt down the appropriate ir_function_signature for the callee.
2. Generate the actual ir_call (assuming we found the callee).

Both of these are complicated.  The first has to handle exact/inexact
matches, lazy importing of built-in prototypes, different scoping rules
for 1.10, 1.20+, and ES.  Not to mention printing a user-friendly error
message with pretty-printed "maybe you meant this" candidate signatures.

The second has to deal with void/non-void functions, pre-call implicit
conversions for "in" parmeters, and post-call "out" call conversions.

Trying to do both in one function is just too unwieldy.  Time to split.

This patch purely moves the code to generate an ir_call into a separate
function and reindents it.  Otherwise, the code is identical.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Paul Berry <stereotype441@gmail.com>