add names for constants in line-map.c

[Manuel LÃpez-IbÃÃez <lopezibanez at gmail dot com>]

This patch adds descriptive names to various constants in line-map.c.

There were some differences between the constants used a various
places, but my understanding is that these differences are arbitrary
and it is easier to understand the code if they are harmonized.

Bootstrapped and regression tested on x86-linux-gnu.

OK?

libcpp/ChangeLog:

2015-05-23  Manuel LÃpez-IbÃÃez  <manu@gcc.gnu.org>

    * line-map.c (LINE_MAP_MAX_COLUMN_NUMBER
    LINE_MAP_MAX_LOCATION_WITH_COLS,LINE_MAP_MAX_SOURCE_LOCATION):
    New constants.
    (linemap_line_start): Use them.
    (linemap_position_for_column): Use them.

Attachment: libcpp-constants.diff
Description: Text document