Remove "eval id" from eval locations

Eval locations (printed in stack traces) contain an useless "eval id" (a sequential number within a Context). The stack traces of exceptions thrown from an eval() thus look something like:

SyntaxError: test/script/basic/es6/const-redeclare-extra.js#36:8<eval>4:2:8 Variable "x" has already been declared

Note that 4:2:8 mean the exception was thrown from line 2, column 8 of the 4th eval in that context. The number 4 seems like it somehow belongs with the line:column information, but is actually completely useless and only serves to confuse. To make things worse, the number changes with the number of recompilations, so with subtle changes to the optimistic typing, the number will also change, rendering a bunch of test cases that uses the "throw from eval" technique to unnecessarily fail, as the expected output from the test case contains this useless number.

It should be removed.