fix identify for some public key pem file that missing object identifier

[machinewu]

I use the following code with python rsa module generate public and private key pem file.

run following code after install python rsa module: pip install rsa

#!/usr/bin/env python
# coding=utf-8

import rsa

pubkey, prikey = rsa.newkeys(1024, poolsize=1)
#print 'pubkey n:\n%s' % pubkey.n
#print 'pubkey e:\n%s' % pubkey.e

print
print 'private key:\n%s' % prikey.save_pkcs1(format='PEM')
print
print 'public key:\n%s' % pubkey.save_pkcs1(format='PEM')

The public key pem file generated is different from using linux openssl generate. For that pem file without object identifier.
We can check it at https://lapo.it.

python rsa generated public key:

-----BEGIN RSA PUBLIC KEY-----
MIGJAoGBAIOf5xGsiGU765gpdsmkqLMTjj5kq5avJAaYssl9R858tnEsHJvfAy9u
aouoPZRtlCCrl0JtqSwf7xAqlLZAsys5Hb++Q9hUDoYAbhEdtzVH5FCzPpSUeOc1
+mal1e8487qUlJvhLjAKvgPJvGcK+KwvZkLvz4OZ0MrBkToNypS5AgMBAAE=
-----END RSA PUBLIC KEY-----


openssl rsa generated public key:

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQChdQAWNIU0WsWLuz6rawY/yD6N
wLcqQDWhh9eLatbJ3JhS7QRW2OzvWvjIWQuqAnqviGmqD+x2jpEfxDIpLck4pRFY
HPLqzhGBPBwBJTY1xi4g9qOH61zxHvY1XafeV/mThh5RGmGa9b2olcSframxHRHT
icm4inwUx2H3lg5fnQIDAQAB
-----END PUBLIC KEY-----

some different for the head and foot:
-----BEGIN RSA PUBLIC KEY-----
different:
-----BEGIN PUBLIC KEY-----

For this PR, I fix it. jsencrypt can work both format.