Partially revert my UB fix in record_line

Partially revert my UB fix in record_line

This reverts the following commit partially:

commit 64dc2d4bd24ff7119c913fff91184414f09b8042
Author: Bernd Edlinger <bernd.edlinger@hotmail.de>
Date:   Thu Mar 12 11:52:34 2020 +0100

    Fix an undefined behavior in record_line

    Additionally do not completely remove symbols
    at the same PC than the end marker, instead
    make them non-is-stmt breakpoints.

We keep the undefined behavoir fix,
but have to restore the original behavior
regarding deletion of the line entries.

2020-04-09  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	revert partially:
	2020-04-01  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        * buildsym.c (record_line): Fix undefined behavior and preserve
        lines at eof.