fix typo in function name

Author: mhegazy

src/compiler/emitter.ts

@@ -1145,7 +1145,7 @@ module ts {
  }
  }
 
- function emitSigatureParamters(node: FunctionDeclaration) {
+ function emitSignatureParameters(node: FunctionDeclaration) {
  write("(");
  if (node) {
  emitCommaList(node.parameters, node.parameters.length - (hasRestParameters(node) ? 1 : 0));
@@ -1154,7 +1154,7 @@ module ts {
  }
 
  function emitSignatureAndBody(node: FunctionDeclaration) {
- emitSigatureParamters(node);
+ emitSignatureParameters(node);
  write(" {");
  scopeEmitStart(node);
  increaseIndent();
@@ -1361,7 +1361,7 @@ module ts {
  emitStart(<Node>ctor || node);
  write("function ");
  emit(node.name);
- emitSigatureParamters(ctor);
+ emitSignatureParameters(ctor);
  write(" {");
  scopeEmitStart(node, "constructor");
  increaseIndent();