Fix a multi-line format-string warning.

Fix a multi-line format-string warning.

GCC 4.5 and 4.6 both issue a warning about the multi-line format
string introduced in bc9c30a0, which also changed the whitespace
in the associated stt file by line-wrapping the long format string.

Instead, use multiple string constants, which the compiler will
concatenate. This maintains the original formatting, but remains
legible within the standard line length.

Change-Id: I27c9f92d46be82d408105a3a4091f145f677e00e