Use correct separator in keywords.txt

The Arduino IDE currently requires the use of a tab separator between the name and identifier. Without this tab the keyword is not highlighted.

Reference:
https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification#keywords

keywords.txt

@@ -23,14 +23,14 @@ MajorPeak	KEYWORD2
 # Constants (LITERAL1)
 #######################################
 
-twoPi LITERAL1
+twoPi	LITERAL1
-fourPi  LITERAL1
+fourPi	LITERAL1
-FFT_FORWARD LITERAL1
+FFT_FORWARD	LITERAL1
-FFT_REVERSE LITERAL1
+FFT_REVERSE	LITERAL1
-FFT_WIN_TYP_RECTANGLE LITERAL1
+FFT_WIN_TYP_RECTANGLE	LITERAL1
-FFT_WIN_TYP_HAMMING   LITERAL1
+FFT_WIN_TYP_HAMMING	LITERAL1
-FFT_WIN_TYP_HANN  LITERAL1
+FFT_WIN_TYP_HANN	LITERAL1
-FFT_WIN_TYP_TRIANGLE  LITERAL1
+FFT_WIN_TYP_TRIANGLE	LITERAL1
-FFT_WIN_TYP_BLACKMAN  LITERAL1
+FFT_WIN_TYP_BLACKMAN	LITERAL1
-FFT_WIN_TYP_FLT_TOP LITERAL1
+FFT_WIN_TYP_FLT_TOP	LITERAL1
-FFT_WIN_TYP_WELCH LITERAL1
+FFT_WIN_TYP_WELCH	LITERAL1