Rename overloads of _mesa_glsl_shader_target_name().

Previously, _mesa_glsl_shader_target_name() had an overload for GLenum
and an overload for the gl_shader_type enum, each of which behaved
differently.  However, since GLenum is a synonym for unsigned int, and
unsigned ints are often used in place of gl_shader_type (e.g. in loop
indices), there was a big risk of calling the wrong overload by
mistake.  This patch gives the two overloads different names so that
it's always clear which one we mean to call.

Reviewed-by: Brian Paul <brianp@vmware.com>
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index a6133ea..f6d7a90 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1375,7 +1375,7 @@
 
    if (main == NULL) {
       linker_error(prog, "%s shader lacks `main'\n",
-		   _mesa_glsl_shader_target_name(shader_list[0]->Type));
+		   _mesa_shader_enum_to_string(shader_list[0]->Type));
       return NULL;
    }