Use objDir (renamed to workDir) for more than just object files.

Rationale: Previous plastering of hash calls and other "unique path"
building all over the code was a manifestation of inconsistency and
code duplication. Now, the hash of the relevant parameters is only
calculated once, and all compile-specific files are stored in that
subdirectory.

Actual object files are now stored in a subdirectory of workDir. The
.rsp file is thus now preserved, because 1) it takes up insignificant
space 2) it's referenced in --chatty output.

This commit also changes the executable file name for generated
executables to no longer include the hash. As a result, users no longer
see the hash as part of the process name in process lists and
pkill/killall tab completion.

This commit also moves the .deps file into the aforementioned work
directory, a suggestion that was raised before.
rdmd: Don't attempt to delete inexisting objDir
rdmd: Ignore existing .deps file with --force
Added missing import std.file to catdoc.d
rdmd: Fix: --force doesn't work with --eval
Merge pull request #24 from Abscissa/master

Fix: RDMD doesn't compile (uses deprecated stuff).
Rearrange catdoc imports in lexicographical order and add module declaration
rdmd: If --force --eval, don't bother to check if the exe already exists.
Merge pull request #25 from Abscissa/fix-force-eval

rdmd: Fix: --force doesn't work with --eval
Merge pull request #21 from JakobOvrum/catdoc

Added missing import std.file to catdoc.d
Merge branch 'master' into rdmd-fixes-20120224

Conflicts:
	rdmd.d
rdmd: --build-only should default to main file dir, not current dir
rdmd: Absent files should indicate a dirty .deps
rel2abs was deprecated
Merge pull request #27 from dawgfoto/master

rel2abs was deprecated
dget script

- use github API to resolve repositories
- either unpack master zipball or clone
Merge pull request #28 from dawgfoto/dget

dget script
Merge branch 'master' into rdmd-fixes-20120224

Conflicts:
	rdmd.d
rdmd: Update comment regarding --build-only
rdmd: Minor --force optimization