Patch: Handle relative paths in .debug_line

[Igor Kovalenko]

I'm willing to devote some time to this problem, as it prevents me from
doing some necessary c++ debugging. So the question is what is currently
more necessary to have this problem fixed:

- Beat the testsuite into accepting one of available patches (e.g. by teaching
   the suite about dwarf2 case or teaching patches to pass the testsuite)

- Have a test case for handling relative paths with dwarf2

Me wrote:
> 
> Also I looked at regressions - this patch makes approximately the same 
> number
> of failures as original relative paths patch. Test case gdb.base/unload.exp
> might show the reason - there seems to be a problem in handling relative 
> paths
> within regression testing scripts:
> 
> Running ../../../gdb-dejagnu/gdb/testsuite/gdb.base/unload.exp ...
> ERROR: couldn't open 
> "../../../gdb-dejagnu/gdb/testsuite/gdb.base/../../../gdb-dejagnu/gdb/testsuite/gdb.base/unloadshr.c": 
> 
> no such file or directory
> FAIL: gdb.base/unload.exp: rerun to shared library breakpoint
> 

The same holds for disassemble failures, I've not checked others yet.
My failure list have:

+FAIL: gdb.base/commands.exp: breakpoint in bp_deleted_in_command_test
+FAIL: gdb.base/commands.exp: breakpoint in temporary_breakpoint_commands
+FAIL: gdb.mi/mi-disassemble.exp: data-disassemble file, line assembly mixed
+FAIL: gdb.mi/mi-disassemble.exp: data-disassemble range assembly mixed
+FAIL: gdb.mi/mi-disassemble.exp: data-disassemble file, line, number assembly mixed
+FAIL: gdb.mi/mi-disassemble.exp: data-disassemble file, line, number (zero lines) assembly mixed
+FAIL: gdb.mi/mi-disassemble.exp: data-disassemble file, line, number (more than main lines) assembly mixed
+FAIL: gdb.mi/mi-file.exp: request path info of current source file (basics.c)
+FAIL: gdb.mi/mi2-disassemble.exp: data-disassemble file, line assembly mixed
+FAIL: gdb.mi/mi2-disassemble.exp: data-disassemble range assembly mixed
+FAIL: gdb.mi/mi2-disassemble.exp: data-disassemble file, line, number assembly mixed
+FAIL: gdb.mi/mi2-disassemble.exp: data-disassemble file, line, number (zero lines) assembly mixed
+FAIL: gdb.mi/mi2-disassemble.exp: data-disassemble file, line, number (more than main lines) assembly mixed
+FAIL: gdb.mi/mi2-file.exp: request path info of current source file (basics.c)

-- 
Kind regards,
Igor V. Kovalenko