Add support for Arch Linux to the easy build script.

As a small aside, add some missing pup packages as well.
Add a C++ implementation of which(1).

As an aside, adjust SConscript to allow building C++11 applications.
Merge pull request #1 from nathan-hoad/nhoad-easy-build-for-arch

Add support for Arch Linux to the easy build script.
Update which to adhere to the style guide.
Use a list for storing aliases and functions for improved insertion time.
More style fixes.
Merge pull request #2 from nathan-hoad/nhoad-which-implementation

Add a C++ implementation of which(1).
build: use -mfpmath=both on x86/x64
posix: don't leak parent process register data to child in execve
x64: fix StackFrame::construct so it complies with the ABI