float textureOffset(sampler2DArrayShadow sampler, vec4 P, ivec2 offset)
was incorrectly requiring the GL_EXT_texture_shadow_lod extension.
NOTE: Prior to GLSL 440, this prototype was defined as
float textureOffset(sampler2DArrayShadow sampler, vec4 P, vec2 offset)
i.e., the type of 'offset' was specified as 'vec2' rather than 'ivec2'.
This is believed to be a typo.
Fixes#3325.