Fix parsing of "==~branch" style dependency version specifiers.
Fix parsing of "==~branch" style dependency version specifiers.

Abscissa/dub,p0nce/dub,schuetzm/dub,Geod24/dub,dreamsxin/dub,D-Programming-Language/dub,gedaiu/dub,Flamaros/dub,alexeibs/dub,xentec/dub,jeanbaptistelab/dub,Abscissa/dub-data-mod,y12uc231/dub,jelmansouri/dub,rjframe/dub,grogancolin/dub,nazriel/dub