Fix a swathe of compiler warnings

Fixes a mixture of mostly harmless warnings in the QextSerialPort and
log4qt libraries.
Minor fixes that clang warns about

Clang complains about different things to gcc; MacOS defaults to
clang.
add various files to .gitignore

Add these to .gitignore:
	GrblController
	*.o
	moc_*.cpp
	qrc_*.cpp
	*.stash
	GrblController-local.iss
Trim diagnostic strings in waitForOk

Trim some diagnostic strings to prevent stray \r's in the log
and better delimit the input in the log entries.
Merge pull request #65 from chrisy/feature/fix-warnings

Fix a bunch of compiler warnings (from Chris)
Merge pull request #66 from chrisy/feature/save-jog-step

Simple patch to save the jog step for the next session (From Chris)
Merge pull request #67 from chrisy/feature/gitignore

add various files to .gitignore (From Chris)
Merge pull request #68 from chrisy/feature/trim-diagnostics

Trim diagnostic strings in waitForOk (From Chris)
Add grbl status icons to mainwindow

- added icon showing spindle state
- added coolant icon
- added tool number and feed rate icons
- refactored the incorrect measurement parser
- cosmetic formatting fixes

Add tool number and feed rate icons