Rollup merge of #43597 - dhduvall:master, r=alexcrichton
Rollup merge of #43597 - dhduvall:master, r=alexcrichton

Fix the Solaris pthread_t raw type in std to match what's in libc

The old type causes failures when building cargo 0.20.0 after rust-lang/libc@8304e06b5.

GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust