glsl/linker: Make get_main_function_signature public

The next patch will use this function in a different file.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>

src/glsl/linker.h

@@ -26,6 +26,9 @@
 #ifndef GLSL_LINKER_H
 #define GLSL_LINKER_H
 
+ir_function_signature *
+link_get_main_function_signature(gl_shader *sh);
+
 extern bool
 link_function_calls(gl_shader_program *prog, gl_shader *main,
 		    gl_shader **shader_list, unsigned num_shaders);