Add a few more legacy inlines for strto*_l.

These three functions are the only reason we need libandroid_support
post-L. Add these so we can remove it entirely for LP64 or users
targeting L+.

Test: make checkbuild
Test: build/soong/scripts/build-ndk-prebuilts.sh
Test: Imported the prebuilts generated from the above to the NDK,
      `./checkbuild.py && ./run_tests.py` with a handful of patches
      to remove libandroid_support for L+.
Bug: None

Change-Id: I39f8ee686bd76ebdb2fc3745b013d56175ba8ff0