js: Set default button pressed for alert boxes correctly.
js: Set default button pressed for alert boxes correctly.

The defaults chosen are the same as in Adobe Acrobat:

nType == 0 (OK) the default pressed button is 1 (OK).
nType == 1 (OK, Cancel) the default pressed button is 2 (Cancel).
nType == 2 (Yes, No) the default pressed button is 4 (Yes).
nType == 3 (Yes, No, Cancel) the default pressed button is 2 (Cancel).

TamirEvan/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf