[m-rev.] changed "no targets specified" message

[Peter Wang]

Hi,

Since commit c2be36780, the compiler prints this error message when
mmc --make is called without a target:

`mercury_compile': *** Error: no targets specified and `MAIN_TARGET' not
  defined.

I prefer how it used to look:

** Error: no targets specified and `MAIN_TARGET' not defined.


Can we change it back? Or remove the `quotes' around mercury_compile,
and fit the whole message on a single line instead of wrapping and
indenting the last word. (At first I thought something had gone wrong
with my terminal emulator.)

I never liked the asterisks either but I understand it's mimicking
GNU make (for whatever reason).

Peter