In c89 mode accept hex fp constants as an extension:

t2.c:1:17: warning: hexadecimal floating constants are a C99 feature
long double d = 0x0.0000003ffffffff00000p-16357L;
                ^

instead of emitting a weird error message that doesn't make sense:

t2.c:1:41: error: hexadecimal floating constants require an exponent
long double d = 0x0.0000003ffffffff00000p-16357L;
                                        ^

rdar://6096838

llvm-svn: 54035