Merge pull request #1862 from abergmeier/prevent_false_negative_in_cache

Prevent Cache.ensure from throwing an error, while the directory already...
add fastcomp externs to asm imports
add dso_handle to library, for fastcomp
send externs to library including
 - fix for structures generated by manually calling generateStructInfo
mkdtemp
check error in mkdtemp()
Document GL_FFP_ONLY setting in src/settings.js.
cleanup and consolidate glGet
Merge branch 'glGet-cleanup' into incoming
Merge pull request #1872 from coolwanglu/mkdtemp

mkdtemp
fix fastcomp vararg alignment, only 4-byte
fix memset return value
fix bitcast type when the input is an llvm function like getelementptr
do not emit empty postsets from js compiler for fastcomp output
fix repeating global_funcs for fastcomp
emit runPostSets call in fastcomp
add missing mkport dependency
fix memmove return value
send EXPORTED_FUNCTIONS to fastcomp glue