The attached patch is a result of discussions here:
    http://sourceware.org/ml/gdb-patches/2012-04/msg00226.html
and here:
    http://sourceware.org/ml/gdb-patches/2012-04/msg00302.html

Code:
2012-04-17  Siva Chandra Reddy  <sivachandra@google.com>

        Add two new methods global_block and static_block to gdb.Symtab
        objects.
        * NEWS (Python scripting): Add entry about the new methods.
        * python/py-symtab.c (stpy_global_block): New function which
        implements the gdb.Symtab.global_block() method.
        (stpy_static_block): New function which implements the
        gdb.Symtab.static_block() method.
        (symtab_object_methods): Add entries for the two new methods.

Testsuite:
2012-04-17  Siva Chandra Reddy  <sivachandra@google.com>

        * py-symbol.exp: Add tests to test the new methods
        gdb.Symtab.global_block() and gdb.Symtab.static_block().
        * py-symbol.c: Add new struct to help test
        gdb.Symtab.static_block().

Docs:
2012-04-17  Siva Chandra Reddy  <sivachandra@google.com>

        * gdb.texinfo (Symbol Tables In Python): Add documentation about
        the new methods global_block and static_block on gdb.Symtab
        objects.

Thanks,
Siva Chandra