Add a test that public headers compile as C99

Makefile

build.yaml

templates/Makefile.template

...s/test/core/surface/public_headers_must_be_c89.c.template

test/core/surface/public_headers_must_be_c89.c

tools/run_tests/sources_and_headers.json

tools/run_tests/tests.json

...ic_headers_must_be_c89/public_headers_must_be_c89.vcxproj

...rs_must_be_c89/public_headers_must_be_c89.vcxproj.filters