[Lazarus] win 32: GDB downgraded to 7.2

[Martin]

On win 32 there is currently a choice between:
- gdb 7.2 (or older)
   does not have http://sourceware.org/bugzilla/show_bug.cgi?id=14018 
which means the debug session can be lost at any time.
   all later versions have this issue.
- gdb 7.3 (which has both known issues...)
- gdb 7.4 / 7.5
   which can set environment vars for the debuggee 
http://sourceware.org/bugzilla/show_bug.cgi?id=10989

There is also an error with stepping, if a library is unloaded (or maybe 
it is a thread being closed). It was observed with 7.4 and 7.5. But as 
it is not reproducible, it is not known, if it will occur with earlier 
versions.
If encountered, the IDE will display a gdb message about being unable to 
set a breakpoint with a negative number.


Otherwise, all Lazarus debugging abilities seem to run equally good on 
7.2 and 7.4/7.5
This should affect all win32 snapshots from tomorrow (including "fixes 
branch"), and all future releases.

Given the choice I decided to go back to 7.2. Since the stability 
affects everyone.

If you need environment, then please keep a copy of 7.4. (All IDE 
changes are usually tested for all gdb 7.x versions)
If you encounter other issues please mail.