Revert "Feature/872 Precompiled headers for g++ (#875)"
Revert "Feature/872 Precompiled headers for g++ (#875)"

This reverts commit 01871542a8385c794c4a1d0b3a435f2f26c120a2.

stan-dev/cmdstan,stan-dev/cmdstan,stan-dev/cmdstan,stan-dev/cmdstan