Remove stray slash, stop on error.
Add frameworks/native to set of header projects and skip non-existent projects.

Bunch of headers were moved from frameworks/base to frameworks/native
in 4.1.1 .
Add android-1.6_r1 platform headers.
Add android-2.0_r1 platform headers.
Add android-2.1_r1 platform headers.
Add android-2.2_r1 platform headers.
Add android-2.3_r1 platform headers.
Add android-2.3.5_r1 platform headers.
Add android-4.0.1_r1 platform headers.
Add android-4.0.4_r1 platform headers.
Add android-4.1.1_r1 platform headers.
Add android-4.2_r1 platform headers.