Permit non-"c99" compiler
Permit non-"c99" compiler

Requires support for '-std=gnu99' and '-x c' so, I think,
gcc and clang will both fly just fine.  The '-x c' requirement
is so the temporary filenames don't leak so much information
into /tmp.

RhysU/c99sh,RhysU/c99sh,RhysU/c99sh,RhysU/c99sh