Added support of `--without-gdb-check` option.

* bootstrap: Added support of `--with-gdb-check` and `--without-gdb-check`
             options.
* jamroot:
  * Added support of `--with-gdb-check` and `--without-gdb-check` options.
  * Added the definition of `GDB_CHECK` global constant.
* gdb/jamfile: Told the build script to skip GDB's `make check` unless
               `GDB_CHECK` is set to `yes`.
Merge pull request #81 from Cryolite/feature/gdbWithoutCheck

Added support of `--without-gdb-check` option.
Added support for irregular version strings of GMP.

* jamroot: Modified regular expressions to accept irregular version strings
           of GMP.
* gmp/latest.sh: Likewise.
* gmp/jamfile: Added build script to rename the top directory of GMP source
               trees in order to fit irregular version strings to ones
               expected in sequel build procedure.
Merge pull request #82 from Cryolite/fix/gmpVersion

Added support for irregular version strings of GMP.
Added a workaround for a bug in GMP configure script.

* gmp/jamfile: Added a workaround for a bug in GMP configure script.
Merge pull request #83 from Cryolite/fix/gmpConfigureWorkaround

Added a workaround for a bug in GMP configure script.
Merge branch 'master' into fix-35