set CFLAGS: -std=gnu99 (fixes SmartOS)

[nshalman]

Fixes the following error message on SmartOS:

$ go get github.com/mattn/go-sqlite3
In file included from /usr/include/stdio.h:37:0,
from go/src/github.com/mattn/go-sqlite3/sqlite3.c:8422:
/opt/local/gcc47/lib/gcc/i386-sun-solaris2.11/4.7.3/include-fixed/sys/feature_tests.h:366:2: error: #error "Compiler or options invalid; UNIX 03 and POSIX.1-2001 applications require the use of c99"

[coveralls]

Coverage remained the same when pulling ae25191 on nshalman:c99 into c9a0db5 on mattn:master.

[mattn]

I wonder this works with clang?

[nshalman]

According do the clang documentation this should be fine. The clang users manual says:

clang supports the -std option, which changes what language mode clang uses. The supported modes for C are c89, gnu89, c94, c99, gnu99, c11, gnu11, and various aliases for those modes. If no -std option is specified, clang defaults to gnu11 mode. Many C99 and C11 features are supported in earlier modes as a conforming extension, with a warning. Use -pedantic-errors to request an error if a feature from a later standard revision is used in an earlier mode.

[mattn]

Thank you.

[nshalman]

Thank you as well!