Alternatively, you'll probably just get it with the #extension GL_EXT_gpu_shader4 : enable you've got in there now, though you'll likely need to call texelFetch2D() instead of texelFetch() (for 2D textures anyway). GLSL 1.3 did away with all the sampler type suffixes from the names of the sampling functions, eliminating a lot of needless function list bloat.
The issue with declaring 1.3 right now if you're using 1.2 (the default IIRC) is that the built-in identifiers (fixed-function shader shims) go away. Which may or may not be more code rework than you want to bite off right now.