Simplify boolean toggling in the TASInputDlg.

Also fixed the indentation for some code in a switch statement.
Fix a typo in DSPSymbols. (DisasssembleRange -> DisassembleRange)

Also remove IsHexDigit and IsAlpha and replace them with their cctype equivalents.
Merge pull request #163 from lioncash/dsp-func-typo

Fix a typo in DSPSymbols. (DisasssembleRange -> DisassembleRange)
Merge pull request #162 from lioncash/tas-dlg

Simplify boolean toggling in the TASInputDlg.