BaseTools/GenFw: Correct datatypes in diagnostic messages and check for string termin...

BaseTools/GenFw: Correct datatypes in diagnostic messages and check for string termination

This patch revises multiple diagnostic messages to use correct
datatypes.  It also checks that a symbol name that is about to be used
in a diagnostic message is terminated by a null character within the
contents of the string table section so that the print routine does
not read past the end of the string table section contents when
reading the symbol name.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael LeMay <michael.lemay@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>