superenv: more help for Autotools with 10.13 SDK on 10.12
superenv: more help for Autotools with 10.13 SDK on 10.12

Add fmemopen and open_memstream to the list of ac_cv_func_*=no symbols
for 10.12 with the 10.13 SDK.

ilovezfs/brew,vitorgalvao/brew,palxex/brew,reelsense/brew,reitermarkus/brew,konqui/brew,DomT4/brew,jmsundar/brew,maxim-belkin/brew,reitermarkus/brew,sjackman/homebrew,mahori/brew,reelsense/brew,mahori/brew,EricFromCanada/brew,JCount/brew,nandub/brew,mgrimes/brew,ilovezfs/brew,MikeMcQuaid/brew,hanxue/linuxbrew,nandub/brew,maxim-belkin/brew,MikeMcQuaid/brew,claui/brew,alyssais/brew,Linuxbrew/brew,aw1621107/brew,Homebrew/brew,mgrimes/brew,pseudocody/brew,DomT4/brew,Linuxbrew/brew,EricFromCanada/brew,DomT4/brew,reitermarkus/brew,mgrimes/brew,Homebrew/brew,Linuxbrew/brew,vitorgalvao/brew,palxex/brew,alyssais/brew,sjackman/homebrew,Linuxbrew/brew,reitermarkus/brew,aw1621107/brew,pseudocody/brew,DomT4/brew,palxex/brew,hanxue/linuxbrew,maxim-belkin/brew,EricFromCanada/brew,claui/brew,sjackman/homebrew,konqui/brew,claui/brew,JCount/brew,Homebrew/brew,JCount/brew,konqui/brew,nandub/brew,MikeMcQuaid/brew,nandub/brew,vitorgalvao/brew,EricFromCanada/brew,Homebrew/brew,pseudocody/brew,aw1621107/brew,JCount/brew,alyssais/brew,claui/brew,mahori/brew,hanxue/linuxbrew,mahori/brew,MikeMcQuaid/brew,reelsense/brew,vitorgalvao/brew,ilovezfs/brew,jmsundar/brew,sjackman/homebrew,konqui/brew,jmsundar/brew