fix #1032: add constants for file open mode

[gms1]

This PR only propagates some missing constants for file open to JavaScript:

Flags For File Open Operations
please see #1032 for a description of possible use cases

[gms1]

tests have passed and the broken Travis CI build has nothing to do with this PR:

 135 passing (12s)
./scripts/build_against_node.sh: line 20: cpp-coveralls: command not found
The command "if [[ "${NODE_VERSION}" ]]; then if [[ "${ELECTRON_VERSION}" ]]; then ./scripts/build_against_electron.sh; else ./scripts/build_against_node.sh; fi; fi" exited with 127.
0.01s$ if [[ "${NODE_VERSION}" -eq "4" ]]; then ./node_modules/.bin/eslint lib; fi;
The command "if [[ "${NODE_VERSION}" -eq "4" ]]; then ./node_modules/.bin/eslint lib; fi;" exited with 0.
Done. Your build exited with 1.

[gms1]

sorry, SQLITE_OPEN_MEMORY seems to be not available

[gms1]

all build errors related to this PR have been fixed, remaining ones are unrelated:

#1012.2:
#1012.3:

make: clang-3.5: Command not found

#1012.10:

./scripts/build_against_node.sh: line 20: cpp-coveralls: command not found

#1012.14:

Updating Homebrew...
==> Downloading https://homebrew.bintray.com/bottles-portable-ruby/portable-ruby-2.3.7.leopard_64.bottle.tar.gz
###############################################################           88.4%######################################################################## 100.0%
==> Pouring portable-ruby-2.3.7.leopard_64.bottle.tar.gz
==>Homebrew is run entirely by unpaid volunteers. Please consider donating:
https://github.com/Homebrew/brew#donations
No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#Build-times-out-because-no-output-was-received
The build has been terminated

#1012.20:

$ sudo -E apt-get -yq --no-install-suggests --no-install-recommends $(travis_apt_get_options) install clang-3.5
...
 The following packages have unmet dependencies:
 clang-3.5 : Depends: libclang1-3.5 (= 1:3.5~svn217304-1~exp1) but it is not going to be installed
             Depends: libllvm3.5 but it is not going to be installed
             Depends: libstdc++-4.8-dev but it is not installable
             Depends: libgcc-4.8-dev but it is not installable
             Depends: libobjc-4.8-dev but it is not installable
             Depends: libclang-common-3.5-dev (= 1:3.5~svn217304-1~exp1) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

[gms1]

replaced by #1078