gdal: Refactor configuration
gdal: Refactor configuration

General cleanup and some specific changes:

  - Now depends on Homebrew's libtiff and libgeotiff now that BigTIFF support
    has landed upstream. This should prevent clashes arising from having
    internal and external copies of these libraries loaded by the same
    executable as noted in Homebrew/homebrew#7054.

  - Add WebP support to the `--complete` option.

  - All backends for which there is no suitable stable formula in core are now
    explicitly listed and disabled using `--without-<backend>` flags during
    configuration. This behavior may be disabled by using the
    `--enable-unsupported` flag which allows configure to drag in any libraries
    that it finds in the user's environment that GDAL enables by default.
    Previously this behavior was a side-effect of the `--complete` option.

filcab/homebrew-core,bfontaine/homebrew-core,ilovezfs/homebrew-core,nbari/homebrew-core,tkoenig/homebrew-core,mfikes/homebrew-core,BrewTestBot/homebrew-core,bigbes/homebrew-core,phusion/homebrew-core,grhawk/homebrew-core,straxhaber/homebrew-core,jabenninghoff/homebrew-core,battlemidget/homebrew-core,Homebrew/homebrew-core,rwhogg/homebrew-core,mbcoguno/homebrew-core,jdubois/homebrew-core,jabenninghoff/homebrew-core,dsXLII/homebrew-core,uyjulian/homebrew-core,cblecker/homebrew-core,FinalDes/homebrew-core,cblecker/homebrew-core,passerbyid/homebrew-core,sjackman/homebrew-core,JCount/homebrew-core,jvillard/homebrew-core,makigumo/homebrew-core,mvbattista/homebrew-core,bfontaine/homebrew-core,gserra-olx/homebrew-core,ShivaHuang/homebrew-core,adam-moss/homebrew-core,zmwangx/homebrew-core,fvioz/homebrew-core,mahori/homebrew-core,aren55555/homebrew-core,kunickiaj/homebrew-core,edporras/homebrew-core,nandub/homebrew-core,Moisan/homebrew-core,jvehent/homebrew-core,BrewTestBot/homebrew-core,Linuxbrew/homebrew-core,bcg62/homebrew-core,lembacon/homebrew-core,kuahyeow/homebrew-core,Homebrew/homebrew-core,nandub/homebrew-core,adamliter/homebrew-core,DomT4/homebrew-core,nbari/homebrew-core,reelsense/homebrew-core,spaam/homebrew-core,forevergenin/homebrew-core,edporras/homebrew-core,smessmer/homebrew-core,robohack/homebrew-core,ylluminarious/homebrew-core,git-lfs/homebrew-core,Linuxbrew/homebrew-core,mvitz/homebrew-core,sdorra/homebrew-core,stgraber/homebrew-core,gserra-olx/homebrew-core,chrisfinazzo/homebrew-core,j-bennet/homebrew-core,jvehent/homebrew-core,jdubois/homebrew-core,git-lfs/homebrew-core,zmwangx/homebrew-core,adamliter/homebrew-core,forevergenin/homebrew-core,jdubois/homebrew-core,lemzwerg/homebrew-core,wolffaxn/homebrew-core,mbcoguno/homebrew-core,uyjulian/homebrew-core,lemzwerg/homebrew-core,ylluminarious/homebrew-core,lasote/homebrew-core,mvitz/homebrew-core,adam-moss/homebrew-core,ilovezfs/homebrew-core,jvillard/homebrew-core,mbcoguno/homebrew-core,zyedidia/homebrew-core,aren55555/homebrew-core,makigumo/homebrew-core,mvbattista/homebrew-core,JCount/homebrew-core,straxhaber/homebrew-core,bigbes/homebrew-core,wolffaxn/homebrew-core,LinuxbrewTestBot/homebrew-core,j-bennet/homebrew-core,sjackman/homebrew-core,jvillard/homebrew-core,andyjeffries/homebrew-core,filcab/homebrew-core,fvioz/homebrew-core,phusion/homebrew-core,mvitz/homebrew-core,passerbyid/homebrew-core,sdorra/homebrew-core,maxim-belkin/homebrew-core,ShivaHuang/homebrew-core,robohack/homebrew-core,kunickiaj/homebrew-core,stgraber/homebrew-core,kuahyeow/homebrew-core,grhawk/homebrew-core,zyedidia/homebrew-core,mahori/homebrew-core,moderndeveloperllc/homebrew-core,moderndeveloperllc/homebrew-core,mfikes/homebrew-core,bcg62/homebrew-core,maxim-belkin/homebrew-core,battlemidget/homebrew-core,aabdnn/homebrew-core,DomT4/homebrew-core,FinalDes/homebrew-core,bcg62/homebrew-core,aabdnn/homebrew-core,wolffaxn/homebrew-core,rwhogg/homebrew-core,lasote/homebrew-core,LinuxbrewTestBot/homebrew-core,dsXLII/homebrew-core,smessmer/homebrew-core,tkoenig/homebrew-core,spaam/homebrew-core,reelsense/homebrew-core,Moisan/homebrew-core,andyjeffries/homebrew-core,lembacon/homebrew-core,chrisfinazzo/homebrew-core,lembacon/homebrew-core