fall back on apropos if help fails; partially fixes #8262

Backport of d31073a7cf912a9e2a6a60b0320941e43f0a7bff
for #8327
additional zeros and ones usages added to manual
added undocumented ones and zeros usage to stdlib

Backport of 6b81eae
for #8387
Correct signbit documentation

Backport of 9fa2c99
ref: #8414
fix typo in faq
Merge pull request #8421 from simon6689/patch-1

fix typo in faq
use https download url for gmp

this was the only dependency url using ftp://

Backport of 8ac035be3a
fix eigfact doc

Backport of 969539267f6dc9d2cf
Document eigenvector format. Closes #8383

- Documentation for eigvecs and eigfact now explain that eigenvectors are stored in columns of F[:vectors].
- Also added output type annotations for eigvecs and eigfact.
- Minor language cleanup
- Add line breaks

Backport of 542cf9d93eaa95e4
update helpdb.jl
Tag v0.3.1
Begin the march toward v0.3.2
backport for #8407, fixes to base/linalg/blas.jl