Rename declareFunction to defineFunction
Rename declareFunction to defineFunction

https://github.com/Khan/KaTeX/pull/262#issuecomment-113981142 indicated a
preference for define over declare.

xymostech/KaTeX,mcanthony/KaTeX,kevinbarabash/KaTeX,Khan/KaTeX,JetStarBlues/KaTeX,xymostech/KaTeX,saschatimme/KaTeX,azotova/KaTeX,mcanthony/KaTeX,Khan/KaTeX,azotova/KaTeX,crepererum/KaTeX,saschatimme/KaTeX,saschatimme/KaTeX,kevinbarabash/KaTeX,JetStarBlues/KaTeX,azotova/KaTeX,kevinbarabash/KaTeX,kwangkim/KaTeX,saschatimme/KaTeX,mcanthony/KaTeX,kwangkim/katex-npm-0.7.0-pre,kwangkim/katex-npm-0.7.0-pre,saschatimme/KaTeX,kwangkim/katex-npm-0.7.0-pre,azotova/KaTeX,kevinbarabash/KaTeX,crepererum/KaTeX,Khan/KaTeX,JetStarBlues/KaTeX,xymostech/KaTeX,kwangkim/katex-npm-0.7.0-pre,mcanthony/KaTeX,kwangkim/KaTeX,mcanthony/KaTeX,crepererum/KaTeX,JetStarBlues/KaTeX,xymostech/KaTeX,kwangkim/KaTeX,xymostech/KaTeX,kevinbarabash/KaTeX,kwangkim/katex-npm-0.7.0-pre,kwangkim/KaTeX,JetStarBlues/KaTeX,crepererum/KaTeX,azotova/KaTeX,crepererum/KaTeX,kwangkim/KaTeX