Stopped supported -0 as a float output because (a) it is non-portable, only existing on some architectures and (b) relies on the undefined behavior of 1.0/0.0

- fixed ANSI (C89) issues, including #418

Converting RUN_TEST() from a macro to a function significantly reduces the size
of the compiled binary.  On amd64, the largest test runner in the test suite
(testsample_DefaultsThroughCommandLine_runner.o) was reduced from 3.4 kB to 2.4
kB (stripped).

cmd.exe does not recognize backslash as an escape character,
leading to errors like the following:

    error: stray '\' in program
    note: in definition of macro 'UNITY_OUTPUT_CHAR_HEADER_DECLARATION'

It does, however, recognize double quotes, so we can use those as
a portable method of escaping special characters on both Windows
and UNIX.

Add TEST_MESSAGE for outputting messages without aborting a test and _MESSAGE variant to TEST_PASS collection.

- Running time macros have been made more portable, previously it was not
  possible to override all macros
- Running time macros will be executed by default test runner, and auto test
  runners
- Adds a default execution time implementation for unix. (Previous default
  implementation only worked on Windows)
- For embedded platforms there is a simple method of getting a default
  implementation by defining a single macro UNITY_CLOCK_MS()
- Removed need for UNITY_EXEC_TIME_RESET. This was not being used for the default
  implementations, if anything ever did need reset-like functionality it could
  simply be wrapped up with the start or stop macros for that platform

 void flushSpy(int c) {}
to:
 void flushSpy(void) {}

The existing implementation was not very good:
 - It printed all very small values as "0.000000..."
 - It did not distinguish positive and negative zero
 - In some cases it printed extra garbage digits for single-precision values
   (e.g. 3.9e+30 was printed as 3.90000013+30)

Tests have been updated to check that we now match printf("%.6g") for
1,000,000 randomly chosen values, except for rounding of the 6th digit.