Fix build of POSIX file descriptor functions

Build Large File System functions for 32bit and 64bit correctly
Fix the detection of the LLVM bitcode compiler. This is now done at KLEE
configure time, not LLVM configure time! Configure will fail without
a working LLVM bitcode compiler. The precedence of detection is as
follows:

1. Compilers set by newly added --with-llvmcc= --with-llvmcxx= configure flags.
2. Clang in LLVM build directory.
3. llvm-gcc in PATH.
4. clang in PATH.

This has been tested with llvm2.9 (llvm-gcc in PATH) and llvm3.3 (clang
built in LLVM build directory).

This addresses a major pain point for new users of KLEE who forget to
put llvm-gcc in their PATH at LLVM configure time and then are later
forced to reconfigure and rebuild LLVM just so KLEE knows the right
PATH!
Merge pull request #65 from delcypher/detect-bitcode-compiler

Support for the detection of the LLVM bitcode compiler in the configure script.
Merge pull request #60 from MartinNowack/fix_posix

Fix build of POSIX file descriptor functions
Fix using assembler addresses for global variables

Format of assembler address strings are different
with newer LLVM version (They don't have a prefix anymore).

This fix takes care of newer LLVM versions (>=3.3) as well.
Fix lseek and getdents

Wrong data types and casts led to wrong values on 64 bit machines
with high values filedescriptor positions.

Fixes DirConsistency and DirSeek test case
Add additional note that testcase might fail if
uclibc is compiled without symbolic printf support
Remove unused testing-dir
Merge pull request #69 from MartinNowack/fix_runtime_posix

Fix runtime posix
Removed testing-env file.  As for testing-dir that was removed in a
prior patch, this is part of the CU experiments and doesn't really
belong here.
Merge branch 'master' of https://github.com/ccadar/klee
Merge pull request #67 from MartinNowack/fix_asm_address

Fix using assembler addresses for global variables