arithmetic parsing error

[Stephen Siegel]

An expression of the form a-b+c gets parsed as a-(b+c):

int m = ((pid+1)*nx)/NP - (pid*nx)/NP + 2
gets parsed as

m : int = (((pid+1)*nx)/NP)-(((pid*nx)/NP)+2);

Please fix and also add simple test for this situation in examples/arithmetic

[ywei]

Fixed. The binary operators now are left associative as they should be.