support linenoise in mirb

Embed small string

.PHONY should be placed after `all'

Fix behavior Hash#eql?

Because some make (e.g. nmake) recognize it as a normal rule definition and if it's the first rule, make runs it as a default rule.
Consequently `all', `test' and `clean' are all ran (because they are depended by .PHONY), and builded files are cleaned.

use flags 4 for *this object is embed*
use flags 8~64 for *embed string length*

Fix build on mingw32

fixed broken gettimeofday implementation for Windows

small, but critical typo :)

Fix and add test for Proc#source_location.

visualcpp toolchain: change compiler/linker flags

error.h: add extern "C" for C++

with these flags visualcpp should behave more like the gcc toolchain

c:
- produce debug information
- optimize for speed instead of disabling optimization
- use non-debug version of Microsoft's C library
- remove unused and unnecessary macro definitions
cxx:
- separate C and C++ (#1594)
- specify kind of exception handling (see warning C4530)
linker:
- produce debug information
- disable incremental linking and re-enable optimizations

__FILE__ test: add support for \ as separator

mruby-time: add gettimeofday(2) for Windows

mruby-time: various smaller changes

small refactor in mirb