Prettify compiler output for verbosity=1
Long lines displaying the invocation of the c compiler are replaced
with short, readable lines.
Tidy up the prettification of the default verbosity c compilation output
Change empty callback into nil
Use defaut nil callback for execProcesses
Forgot to keep extern pragma for execProcesses
Merge pull request #1569 from idlewan/prettyCC

Prettify compiler output for verbosity=1