Base documentation - minor revisions

Many revisions on the base.rst. Formated and added new examples, inserted some returned types, etc.
Added FAQ entry on function argument semantics

Added an entry about passing arguments to functions.
Corrections on base.rst previous commit

Removed type annotation of some functions
Revision of the last commit on FAQ
Minor revision
Typo

Fixed a typo
Added introduction to variables to the manual

Simple explanation about variables
Fixed typo
Changed examples comments

Formated the comments to match the rest of the manual
optimize large array deserialization from async streams
Corrected returned value
Only purge sys.$(SHLIB_EXT) if JULIA_CPU_TARGET == native
Merge pull request #6875 from brk00/patch-6

Added introduction to variables to the manual
Changed "constant" to "immutable object"
Update for LLVM35 changes
Makefile: DEBUG -> JL_DEBUG_BUILD to avoid LLVM conflict
Add code_native support for MCJIT
Add partial support for line info.

Use ';' as separator in LLVM function name, and add jl_demangle
Merge pull request #6868 from brk00/patch-5

Added FAQ entry on function argument semantics
Solve generalized eigen-problem with eigs (Fix #6758)
Remove complexOP keyword argument, as I believe it was not used correctly.
Update docs and add tests.