Copy-paste error fix and added installation of inl files.

When defining MATH_ENABLE_UNCOMMON_OPERATIONS I noticed that there were duplicate definitions of some of those extra operators in float2.h and float4.h. It looked like a typo where someone copied the code rather than moved it so I deleted the duplicate entries.

Additionally, I added a line to the CMakeLists.txt which installs *.inl files alongside the headers.