Add n_digits=101 precision boundary tests

Addresses dtoa.c TODO item: 'test n_digits=101 instead of 100'

Author: jiangjieke

dtoa.c

@@ -37,7 +37,6 @@
 
 /* 
    TODO:
-   - test n_digits=101 instead of 100
    - simplify subnormal handling
    - reduce max memory usage
    - free format: could add shortcut if exact result

tests/test_builtin.js

@@ -442,6 +442,15 @@ function test_number()
 
     assert((1.3).toString(7), "1.2046204620462046205");
     assert((1.3).toString(35), "1.ahhhhhhhhhm");
+
+    assert((123.456).toExponential(100),
+           "1.2345600000000000306954461848363280296325683593750000000000000000000000000000000000000000000000000000e+2");
+    assert((1.23e-99).toExponential(100),
+           "1.2299999999999999636794326616259654935901564299639709630577493044757187515388707554223010856511630028e-99");
+    assert((-0.0007).toExponential(100),
+           "-6.9999999999999999288763374849509091291110962629318237304687500000000000000000000000000000000000000000e-4");
+    assert((0).toExponential(100),
+           "0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000e+0");
 }
 
 function test_eval2()