Wrote documentation for functions found in the value.h file.

Added documentation of more of the C API functions found inside mruby.h

fix masgn nosplat array rhs bug

The rest lhs variable has to be an empty array if rhs is an array with
less elements than pre + post lhs variables. The codegen generated
OP_ARRAY with an invalid length (such as 127 for *a, b = []) because rn
was negative.

Merge branch 'failing-multiple-assignments-with-rest-tests' of https://github.com/cremno/mruby into cremno-failing-multiple-assignments-with-rest-tests

check if outer is a class or module

codegen: remove unreachable code

For modules this check didn't exist yet. Also call #inspect.

It's just a copy of the code in the previous case (NODE_CALL).

fix capture group index bug

mruby.h: simplify ctype-like macros

atoi() is used to convert the index to an int but the behavior is
undefined if the value can't be represented.

> $9999999999
00007 NODE_SCOPE:
00007   NODE_BEGIN:
00007     NODE_NTH_REF: $2147483647
irep 00630580 nregs=2 nlocals=1 pools=0 syms=1 reps=0
file: (mirb)
7 000 OP_GETGLOBAL  R1      :$2147483647
7 001 OP_STOP

Call strtoul() instead as its behavior in such cases is defined and add
a simple range check.

Alternatively NODE_NTH_REF's cdr could be changed from int to mrb_sym
(like NODE_GVAR).

Not needed anymore since 85075bef

Reduces the file size (by up to 2 KB with VS2015 RC, /O2, /MD) and
removes the requirement of including <ctype.h> before their usage.
Multiple macro argument evaluation and lack of type-checking is still an
issue.

Move "src/mrb_throw.h" to "include/mruby/throw.h".

Related to #2760.

Move `mrb_codedump_all` to "src/codedump.c".

Add null check on lex_strterm in heredoc block

Related to #2760.

Add locals null checks

Verify that proc_lambda is passed a proc

remove an always-true conditional.