Shader: Initial implementation of x86_x64 JIT compiler for Pica vertex shaders.

- Config: Add an option for selecting to use shader JIT or interpreter.
- Qt: Add a menu option for enabling/disabling the shader JIT.

src/citra/default_ini.h

@@ -42,6 +42,10 @@ frame_skip =
 # 0 (default): Software, 1: Hardware
 use_hw_renderer =
 
+# Whether to use the Just-In-Time (JIT) compiler for shader emulation
+# 0 : Interpreter (slow), 1 (default): JIT (fast)
+use_shader_jit =
+
 # The clear color for the renderer. What shows up on the sides of the bottom screen.
 # Must be in range of 0.0-1.0. Defaults to 1.0 for all.
 bg_red =