ART fix oat debug source map operations

Several places need to be fixed in OAT debug source map generation
(see comments in https://android-review.googlesource.com/#/c/102610/19/compiler/compiled_method.h

):
1. Source Maps are deduplicated in Compiler Driver by implicit conversion
   SrcMapElems to bytes. This implies incorrect operator==.
2. SrcMapElem operator < is peculiar, and cannot be applied to
   SrcMapElems with negative to_ fields
3. SrcMap.Arrange method is not elegant

The fix is to introduce explicit conversion from SrcMapElem to one
signed 64-bit value, which is used as a base of two new operators < and ==.
They are correct and intuitive. DedupeHashFunc is changed to
explicitly convert array elements to byte, so the explicit type conversion
from SrcMapElem to byte is used.

Minor fix: In Line Table Programs the file index set command is generated
only if the index gets new value.

Change-Id: I5e2c03404a437254fc2db3485b22bfc1799b39b7
Signed-off-by: Yevgeny Rouban <yevgeny.y.rouban@intel.com>