docs: Add 1.4 index to the API references
docs: Add 1.4 index to the API references

Now that master has branched for the 1.3 development cycle.

spatulasnout/cogl,djdeath/cogl-android,spatulasnout/cogl,djdeath/cogl,djdeath/cogl,djdeath/cogl,Distrotech/cogl,djdeath/cogl-android,gcampax/cogl,Distrotech/cogl,gcampax/cogl,gcampax/cogl,collects/cogl,collects/cogl,Distrotech/cogl,djdeath/cogl-android,Distrotech/cogl,gcampax/cogl