Fixed invalid assumption that "char" type is signed.

Nothing in any C++ standard guarantees that "char" is signed (when compiling for ARM, for instance, it is typically unsigned).
Added generic version of get_clock_cycles for use on architectures without the "rdtsc" instruction.

The generic implementation of get_clock_cycles uses clock_gettime from time.h to get time measured in nanoseconds, then assumes that 1 nanosecond = 1 clock cycle (it does, at 1GHz).
Set the cluster_arch_bitsize to "32bit" on ARM.
Implemented coroutine context-switching for ARM.
ARM in configure
Add some cross-compiling support to the configure script
Add boost to fetch list
Improve cross-compiling support in configure script
Add missing quotes
Allow cross-compiling libprotobuf
Allow cross-compiling protoc and v8
Make termcap conditional
Add missing boost.sh file
Remove UNUSED macro
Improve cross-compiling
Fix undefined variable in configure
Properly fix undefined variable in configure
Improve version detection in configure script
Fix build rules for dependencies when cross-compiling